Allergies: The Complete Guide

Key numbers at a glance

What an allergy actually is

An allergy is your immune system treating something harmless as if it were a threat. Pollen, a food protein, a dog's skin flakes or a bee's venom is not dangerous in itself. In an allergic person, the immune system has learned to make a specific antibody, called immunoglobulin E or IgE, against that substance. Those antibodies sit on the surface of mast cells in your skin, airways and gut, waiting. When the trigger turns up again, it binds to the IgE and the mast cells release histamine and other chemicals within minutes.

Those chemicals cause everything you recognize as an allergic reaction. Blood vessels widen and leak, which produces swelling, hives and, in a severe reaction, a drop in blood pressure. Smooth muscle in the airways tightens, which causes wheeze. Nerve endings are irritated, which causes itching and sneezing. Mucus production increases, which gives you the runny nose. The same basic chain explains a mild itchy eye in June and a life-threatening reaction to peanut; the difference is how much of the body is involved and how fast.

The first exposure to an allergen does not usually cause a reaction. It is the step where the body becomes sensitized, quietly producing IgE. Reactions come on later exposures. This is also why a test can show IgE to something you eat every day without any problem: being sensitized is not the same thing as being allergic, a distinction that matters a great deal when it comes to testing.

Allergy, intolerance and side effects are different things

People use the word allergy loosely, and the confusion causes real harm in both directions. A food intolerance, such as lactose intolerance, is a digestive problem: it causes bloating, gas or diarrhea, depends on the amount eaten, and does not involve IgE or carry a risk of anaphylaxis. A side effect of a medicine, such as nausea from an antibiotic, is a predictable effect of the drug rather than an immune reaction. Calling these allergies can lead to unnecessary restrictions, while dismissing a true allergy as an intolerance can lead to a dangerous re-exposure.

The main kinds of allergy

Allergies are grouped by the trigger and by where in the body they show up. Many people have more than one, because the tendency to make IgE, called atopy, runs in families and tends to show up in several ways over a lifetime. A child with eczema in infancy may go on to develop food allergy, then hay fever and asthma, a sequence often described as the atopic march. Not every child follows it, and many outgrow some allergies, particularly to milk and egg.

Knowing which group your symptoms fall into tells you what kind of help you need. Seasonal sneezing is usually managed with your doctor or pharmacist; a reaction involving breathing after a food or sting needs an allergist and an emergency plan. The timing of symptoms is a useful clue: IgE reactions usually begin within minutes to a couple of hours of exposure, while contact rashes and some drug rashes appear a day or more later.

• Allergic rhinitis (hay fever): sneezing, itchy and runny nose and itchy eyes from pollen, or year-round from dust mites, pets or mold.
• Food allergy: reactions within minutes to about two hours of eating a food, from hives and vomiting to anaphylaxis.
• Drug allergy: an immune reaction to a medicine, from a rash to anaphylaxis or, rarely, severe skin reactions.
• Insect sting allergy: reactions to bee, wasp, hornet, yellow jacket or fire ant venom.
• Allergic asthma: asthma symptoms driven by inhaled allergens.
• Atopic dermatitis (eczema): a skin barrier condition closely linked to allergy but not caused by it in most people.
• Contact allergy: a delayed, itchy rash where the skin touched something such as nickel or certain fragrances, which works through a different immune pathway.

Anaphylaxis: recognizing it and acting fast

Anaphylaxis is a severe allergic reaction that affects breathing or circulation, and it can become life-threatening within minutes. It is the single most important thing in this guide, because the treatment is simple and the main cause of death is delay. The signs usually start within minutes of exposure, sometimes up to an hour or two after food. Skin symptoms such as hives and flushing are common, but they are absent in some reactions, so their absence does not mean a reaction is mild.

The first-line treatment is intramuscular epinephrine, injected into the outer thigh with an auto-injector. It can go through clothing. Epinephrine tightens blood vessels, raises blood pressure, relaxes the airways and reduces swelling, which is exactly what the body needs. If there is no improvement after 5 to 15 minutes, a second dose is given, which is why people at risk carry two. An epinephrine nasal spray has also been approved by the FDA for some people; your allergist can tell you whether it suits you.

Antihistamines do not treat anaphylaxis. They can ease hives and itching, but they act too slowly and do nothing for a falling blood pressure or a closing airway. Reaching for an antihistamine first and waiting to see is one of the most common and dangerous mistakes. The same goes for an asthma inhaler: it may help wheeze, but it does not replace epinephrine.

• Swelling of the lips, tongue or throat, or a feeling of the throat closing
• Difficulty breathing or swallowing, wheeze, persistent cough or a hoarse voice
• Dizziness, faintness, confusion, pale and floppy (in a young child) or collapse
• Widespread hives or flushing together with any of the above
• Vomiting and stomach pain after an insect sting, or with other symptoms after a food

What to do, in order

Use the epinephrine auto-injector immediately. Then call 911 and say the word anaphylaxis. Lie the person flat with their legs raised; if breathing is difficult, let them sit up, and if they are pregnant, lay them on their left side. Do not let them stand up or walk, even if they feel better, because a sudden change of position can cause blood pressure to collapse. Give a second dose after 5 to 15 minutes if there is no improvement. Go to the emergency room every time, even if symptoms settle, because a second wave of symptoms can follow hours later.

Hay fever and indoor allergies

Allergic rhinitis is by far the most common allergy, and it is easy to underestimate. Constant congestion disrupts sleep, concentration and work, and in people with asthma, uncontrolled nasal allergy often makes the chest worse. In the US, tree pollen tends to dominate in spring, grass pollen in late spring and summer, and ragweed in late summer and fall, although timing varies by region. Year-round symptoms point more toward dust mites, pet dander, cockroaches or mold.

The most effective single treatment for nasal symptoms is an intranasal corticosteroid spray, many of which are sold over the counter. It is also the treatment people use least well. These sprays reduce inflammation rather than blocking histamine, so the effect builds over days to weeks of daily use. People often try one for two days, decide it does not work and give up. For seasonal allergy, starting a week or two before your usual season, and using it every day through the season, works far better than using it only on bad days.

Technique matters. Tilt your head slightly forward, put the nozzle just inside the nostril, aim it toward the outer side of the nose, away from the central septum, and sniff gently rather than hard. Aiming at the septum causes irritation and nosebleeds, which is the usual reason people stop. Non-sedating antihistamine tablets help with sneezing, itching and watery eyes and are suitable for daytime use. Older sedating antihistamines cause drowsiness that can affect driving and work the next day, even when you do not feel sleepy.

Reducing exposure at home

On high-pollen days, keep windows closed, shower and change clothes after being outdoors, and dry laundry indoors or in a dryer. For dust mites, wash bedding weekly in hot water of at least 130°F (54°C), use mite-proof covers on pillows and mattresses, and keep indoor humidity below 50 percent, because mites thrive in humid air. Fix leaks and damp areas promptly to limit mold. Be realistic about what avoidance achieves: the evidence that dust mite measures alone improve symptoms is weaker than most people assume, so they work best alongside proper treatment, not instead of it. Judge any measure by whether your symptoms actually change.

Food allergy

Food allergy is an immune reaction to a protein in a food, usually IgE-mediated, which is why reactions tend to start quickly, from a few minutes to about two hours after eating. Symptoms range from hives, lip swelling and vomiting to anaphylaxis. The severity of past reactions does not reliably predict the next one, which is why anyone with a confirmed IgE food allergy is usually prescribed epinephrine.

Under US law, nine major food allergens must be declared on packaged food labels: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame. Sesame was added most recently, so older guidance may list eight. The allergen must appear either in the ingredient list by its common name or in a "Contains" statement. Read the label every time you buy a product, even a familiar one, because recipes and factories change without notice.

Precautionary statements such as "may contain" or "made in a facility that also processes" are voluntary and are not defined by law. That means their absence does not prove a product is safe and their presence does not tell you how much risk there is. Do not assume "may contain" means a product is probably fine. Restaurants are not covered by packaged-food labeling rules, so tell staff clearly about your allergy, ask how food is prepared, and ask about cross-contact from shared fryers, grills, utensils and surfaces.

Introducing allergenic foods to babies

Guidance on infants has reversed from what many parents were told in the past. Delaying allergenic foods does not prevent allergy and may increase risk. US guidelines from the National Institute of Allergy and Infectious Diseases recommend introducing peanut-containing foods early. For infants at high risk, meaning those with severe eczema, egg allergy or both, introduction is recommended around 4 to 6 months of age, after talking with your pediatrician, who may suggest testing or a supervised first feed. Never give whole peanuts or chunks of peanut butter to young children, because they are a choking hazard; use thinned peanut butter or peanut powder mixed into food.

Pollen food syndrome

Some people with pollen allergy get an itchy mouth or throat from certain raw fruits, vegetables or nuts, because the proteins resemble pollen proteins. Symptoms are usually confined to the mouth and often disappear when the food is cooked. It is generally mild, but mention it to your doctor, especially if symptoms ever go beyond the mouth.

Allergy testing: what it can and cannot tell you

The two main allergy tests are skin prick testing, where a tiny amount of allergen is pricked into the skin and the reaction measured after about 15 minutes, and blood tests that measure specific IgE to a particular substance. Both are useful, and both measure sensitization, not allergy. A positive result means you have made IgE to the substance. Whether that translates into symptoms is a separate question that only your history, and sometimes a supervised challenge, can answer.

This is why testing must be guided by history rather than the other way round. If you eat wheat daily without problems, a positive wheat test does not mean you should stop eating it. Large panels of tests ordered without a clear story produce false positives, which lead to unnecessary restrictions, anxiety and, in children, poor nutrition. Some antihistamines interfere with skin testing, so ask before your appointment whether you should stop any medicines and for how long.

When the answer is unclear, the most reliable test is a supervised oral food challenge: eating gradually increasing amounts of the food in a clinic with staff and emergency treatment on hand. It sounds alarming, but it is how allergists confirm or rule out an allergy, and it often frees people to eat foods they have avoided for years. Never try this at home with a food you have reacted to.

• Useful: a detailed history, skin prick tests, specific IgE blood tests, and supervised oral challenges, interpreted by a board-certified allergist.
• Not recommended: IgG food panels, hair analysis, applied kinesiology, electrodermal or "bioresonance" testing, sold directly to the public.
• Bring to your appointment: what you ate or were exposed to, how much, how quickly symptoms started, what they were, how long they lasted and what treatment you needed.

Drug allergy and the penicillin label

A drug allergy is an immune reaction to a medicine, and it is different from a side effect. Nausea or diarrhea from an antibiotic, a headache from a blood pressure medicine or drowsiness from an antihistamine are side effects, not allergies, and should be described that way when you give your history. True drug allergy can cause hives, swelling, wheeze or anaphylaxis, usually soon after a dose, or delayed rashes days into a course.

Penicillin is the most commonly recorded drug allergy, and most people with that label are not actually allergic, according to the CDC. Some never were; the rash in childhood may have been caused by the infection itself. Others were allergic once and the sensitivity has faded over the years. The label is not harmless. People labeled penicillin-allergic are often given broader or less effective antibiotics, which are linked to worse outcomes, more side effects and more antibiotic resistance.

Allergists can assess a penicillin label with a careful history and, where appropriate, skin testing and a supervised test dose. Many people have the label removed this way. If yours is limiting your treatment, or you are not sure why it is on your record, ask your doctor about an allergy evaluation. If you do have a confirmed drug allergy, keep a written record of the medicine, the reaction and the date, and make sure every pharmacy and clinic you use has it.

Rare but serious skin reactions

A small number of drug reactions affect the skin and mucous membranes severely, such as Stevens-Johnson syndrome. Warning signs include a widespread rash, blistering, skin peeling, sores in the mouth or eyes, and fever with a rash, typically starting days to weeks after a new medicine. Stop the medicine and contact your doctor urgently or go to the emergency room.

Insect stings

Most sting reactions are local: pain, redness and swelling at the site. A large local reaction, where the swelling spreads across much of a limb over a day or two, is common and alarming but is not anaphylaxis, and it does not by itself mean the next sting will be dangerous. A cold compress, elevation and an oral antihistamine usually help. Spreading redness, warmth and fever in the days afterward suggest infection and need a doctor.

What matters is a systemic reaction, meaning symptoms away from the sting site: hives elsewhere on the body, swelling of the face or throat, wheeze, dizziness or collapse. That is anaphylaxis and needs epinephrine and 911. If you are stung by a bee, scrape the stinger out sideways with a fingernail or card as soon as possible rather than pinching it, which can squeeze more venom in. Stings inside the mouth or throat need urgent assessment for anyone, allergic or not, because local swelling there can block the airway.

After any systemic reaction to a sting, ask for referral to an allergist about venom immunotherapy. This is a course of injections of gradually increasing doses of purified venom, and it substantially reduces the risk of a severe reaction to future stings. It is one of the most effective treatments in allergy medicine and is underused, partly because people do not know it exists.

Asthma, eczema and the allergic family of conditions

Allergy and asthma are closely linked. Pollen, dust mites, pet dander and mold are among the most common reasons asthma control slips, and treating allergic rhinitis properly often improves asthma symptoms too, because the nose and lungs form one connected airway. Keep taking your controller inhaler through allergy season rather than stopping when you feel well. Needing your quick-relief inhaler more than 2 days a week, or waking at night with symptoms, is a sign asthma is not well controlled and should be reviewed by your doctor.

Some medicines can trigger asthma in susceptible people, notably aspirin and other NSAIDs such as ibuprofen, and beta blockers, including some eye drops. If any of these has made your breathing worse before, tell every doctor and pharmacist you see. A written asthma action plan, agreed with your doctor, tells you what to take day to day, what to do when symptoms worsen, and when to call 911.

Eczema, or atopic dermatitis, is primarily a skin barrier condition. Food allergy is relevant in a minority, mainly infants with severe eczema that does not respond to good skin care. The foundation of treatment is generous, regular moisturizer and topical steroids used at the strength and for the time prescribed. Under-treating because of fear of steroids is common and keeps eczema active. Cutting foods from a child's diet because of eczema, without assessment, risks poor nutrition and may even increase the chance of developing food allergy, so involve your pediatrician and a registered dietitian before any elimination diet.

Treatment options, from the pharmacy to the allergist

Most allergy treatment controls symptoms rather than changing the allergy itself, and that is perfectly reasonable for many people. Over-the-counter options include steroid nasal sprays, non-sedating antihistamine tablets and antihistamine eye drops. Saline rinses can help clear the nose. Decongestant sprays give quick relief but cause rebound congestion if used for more than a few days, and oral decongestants can raise blood pressure and heart rate, so check with a pharmacist if you have high blood pressure, heart disease, glaucoma or prostate problems. Prescription options include combination nasal sprays and leukotriene receptor antagonists such as montelukast, which carries an FDA warning about mood and behavior changes that you should discuss with your doctor.

Allergen immunotherapy is the only approach that changes how your immune system responds. Allergy shots involve regular injections of gradually increasing doses of the allergen, then maintenance doses typically continued for 3 to 5 years, with benefits that can last after stopping. They are given in a medical office because of a small risk of reaction, and you wait afterward to be observed. For grass, ragweed and dust mite allergy, FDA-approved tablets that dissolve under the tongue are an alternative for some people, with the first dose taken under medical supervision.

For food allergy, options have grown. An FDA-approved oral immunotherapy product for peanut allergy is available for some children, and a biologic medicine, omalizumab, is approved to reduce the risk of reactions from accidental exposure to some foods. Neither is a cure, both still require avoidance and carrying epinephrine, and both involve trade-offs your allergist will discuss. For severe asthma and eczema, several other biologic medicines are now available.

Pregnancy and breastfeeding

Do not stop asthma controller medicines because you are pregnant; poorly controlled asthma is a greater risk to you and your baby than the medicines. Ask your obstetrician or pharmacist which allergy treatments are suitable, because the evidence differs between medicines. Oral decongestants are generally avoided early in pregnancy. Epinephrine is still the treatment for anaphylaxis in pregnancy.

Children

Children need age-appropriate products and doses; check the label and ask your pediatrician or pharmacist rather than giving a fraction of an adult medicine. Epinephrine auto-injectors come in doses matched to weight, so your child's prescription needs updating as they grow.

Older adults

Older sedating antihistamines, such as diphenhydramine, can cause confusion, constipation, urinary retention and falls in older adults and are generally best avoided. They are also hidden in many nighttime cold and sleep products. Ask a pharmacist to check allergy medicines against your other prescriptions.

Living with a severe allergy

Most fatal allergic reactions involve a delay in giving epinephrine, and most of those delays are practical: the auto-injector was at home, it had expired, nobody nearby knew how to use it, or someone hoped symptoms would settle. Living safely with a severe allergy is therefore mostly about systems. Carry two auto-injectors everywhere, including short trips. Keep them out of hot cars and freezing conditions. Check expiration dates and set a reminder to refill well before they lapse.

Have a written anaphylaxis action plan from your doctor and share it with your child's school or child care, your workplace if you choose, and close family and friends. Teach the people around you how to use the device with a trainer pen. Medical identification jewelry or a wallet card helps strangers and paramedics act quickly. Children with food allergy are often eligible for a Section 504 plan at school, which formally sets out the accommodations they need.

Plan ahead for travel and eating out. Carry your devices in your hand luggage, bring a copy of your action plan, learn how to say your allergy in the local language when abroad, and know the local emergency number. Ask restaurants about ingredients and preparation every time, and be prepared to leave if the answers are vague. When flying, contact the airline in advance about its allergy policy and keep your devices with you rather than in the overhead bin.

Cost and access in the US

Epinephrine devices can be expensive, which leads some people to carry one instead of two or to keep expired devices. Generic auto-injectors are available and are usually cheaper; ask your pharmacist about them and about manufacturer savings programs. Check your plan's formulary, since covered devices differ between insurers. Medicaid covers prescribed epinephrine, and allergy evaluation and immunotherapy are covered by most plans with a referral or prior authorization. Do not let cost lead you to go without; your doctor, pharmacist or insurer can help you find the least expensive covered option.

Myths, your doctor and a yearly plan

A few myths cause a lot of harm. Antihistamines do not treat anaphylaxis. A mild reaction last time does not guarantee a mild reaction next time. Commercial IgG and hair tests do not diagnose allergy. Being labeled penicillin-allergic is not necessarily for life. Eczema is not usually caused by food. Local honey has not been shown to treat hay fever. And moving to a different climate rarely solves pollen allergy for long, because people often become sensitized to the local plants.

When you see your doctor, describe what happened as precisely as you can: the trigger, how much, how quickly symptoms began, which parts of the body were involved, and what treatment you needed. Ask directly whether you need epinephrine, whether you should see a board-certified allergist, and whether immunotherapy is an option for you. If you have asthma as well as allergy, ask for both to be reviewed together.

A simple yearly routine keeps everything current, and it matters because allergies change: children outgrow some, adults develop new ones, and devices and doses go out of date. Each year, review your action plan with your doctor or allergist, replace expired auto-injectors, update your child's dose as they grow, retrain family members, school and coworkers, and start your nasal spray before your pollen season begins.

• Two to four weeks before your pollen season: start daily steroid nasal spray and check you have antihistamines at home.
• At the start of each school year: refill auto-injectors, update the action plan and school forms, and check the 504 plan if your child has one.
• Every month: glance at expiration dates and make sure both devices are in your bag.
• Once a year: review asthma control, medicines and any new reactions with your doctor, and ask whether a penicillin label or an old food restriction should be reassessed.

Every guide in this topic

• Anaphylaxis: What Published Guidance Supports
• Food Allergy: What the Evidence Actually Says
• What the Guidance Really Says About Hay Fever and Pollen
• Allergy Testing: What Published Guidance Supports
• Drug Allergy: Sorting the Evidence From the Noise
• What the Guidance Really Says About Asthma and Allergy
• Eczema and Allergy: What Published Guidance Supports
• What the Guidance Really Says About House Dust Mite
• What the Guidance Really Says About Insect Stings
• The Evidence on Living with Severe Allergy, Without the Hype

Frequently asked questions

Can I just take an antihistamine if I think I am having anaphylaxis?

No. Antihistamines can ease itching and hives, but they act too slowly and do nothing for a falling blood pressure or a swelling airway. If you have signs of anaphylaxis, such as throat swelling, difficulty breathing, wheeze, faintness or collapse, use your epinephrine auto-injector immediately, call 911, and lie flat with your legs raised unless breathing is difficult.

Why do I need to go to the emergency room if the epinephrine worked?

Epinephrine wears off, and symptoms can return hours later even after a full recovery, a pattern called a biphasic reaction. In the emergency room you can be observed, given further treatment if needed, and sent home with a plan. Always call 911 after using epinephrine, and do not drive yourself.

Is a food intolerance the same as a food allergy?

No. A food intolerance, such as lactose intolerance, is a digestive problem that causes symptoms like bloating or diarrhea, usually depending on how much you eat. It does not involve the immune system in the same way and does not cause anaphylaxis. A food allergy is an immune reaction that can be severe even with small amounts, and it needs proper diagnosis.

Are the food sensitivity tests sold online worth doing?

Allergists do not recommend them. IgG panels, hair analysis and similar tests do not diagnose food allergy or intolerance, and they often lead people to cut out healthy foods unnecessarily. If you suspect a food allergy, ask your doctor for referral to a board-certified allergist, who will use your history to decide which tests, if any, are useful.

My steroid nasal spray does not seem to work. Should I stop?

Give it time and check your technique. Steroid sprays build up their effect over days to weeks of daily use, so judging one after two days is too soon. Aim the nozzle toward the outer side of your nose, away from the central septum, and sniff gently. If symptoms are still uncontrolled after a few weeks of correct daily use, see your doctor.

I was told I was allergic to penicillin as a child. Am I still?

Possibly not. Most people labeled penicillin-allergic turn out not to be allergic when properly assessed, either because the original rash had another cause or because the sensitivity has faded. The label can lead to less effective antibiotics, so ask your doctor about an evaluation by an allergist, who can often confirm whether it can safely be removed.

When should my baby first have peanut?

US guidelines recommend introducing peanut early rather than delaying it. Babies at high risk, meaning those with severe eczema or egg allergy, should be introduced around 4 to 6 months after talking with your pediatrician, who may arrange testing or a supervised first feed. Use thinned peanut butter or peanut powder in food, never whole peanuts, which are a choking hazard.

Does a big swelling after a bee sting mean I am allergic?

A large local reaction, with swelling spreading around the sting over a day or two, is common and is not anaphylaxis. What matters is symptoms away from the sting, such as hives elsewhere, throat swelling, wheeze or dizziness. Those need epinephrine and 911. Afterward, ask your doctor about referral for venom immunotherapy, which greatly reduces the risk of future severe reactions.

Do allergy shots really work, and how long do they take?

For the right person, yes. Allergy shots are the main treatment that changes how your immune system responds rather than just easing symptoms. They start with a build-up phase and then maintenance injections, usually continued for 3 to 5 years, and benefits can last after stopping. They are given in a medical office because of a small risk of reaction.

Is it safe to take allergy medicines while pregnant?

Some are considered suitable and some are best avoided, so ask your obstetrician or pharmacist before starting or continuing anything. Do not stop asthma controller medicines without advice, because uncontrolled asthma is riskier than the medicines. Oral decongestants are generally avoided in early pregnancy. If anaphylaxis occurs during pregnancy, epinephrine is still the correct treatment.

When to speak to a doctor

Call 911 immediately for swelling of the lips, tongue or throat, difficulty breathing or swallowing, a hoarse voice, wheeze, widespread hives with faintness, or collapse; use an epinephrine auto-injector straight away if one is prescribed, lie the person flat with legs raised, and always go to the emergency room afterward. Call 911 if an asthma reliever is not helping or someone is too breathless to speak in full sentences. Go to the emergency room or contact your doctor urgently for a widespread blistering or peeling rash, or mouth or eye sores, after a new medicine. See your doctor for referral to an allergist after any reaction involving breathing or circulation, for allergy symptoms not controlled by regular treatment, or for asthma that worsens in allergy season.

Where this comes from

• American Academy of Allergy, Asthma & Immunology — Anaphylaxis
• American Academy of Allergy, Asthma & Immunology — Rhinitis (Hay Fever)
• American Academy of Allergy, Asthma & Immunology — Allergy Testing
• National Institute of Allergy and Infectious Diseases — Food Allergy
• National Institute of Allergy and Infectious Diseases — Addendum Guidelines for the Prevention of Peanut Allergy in the United States
• FDA — Food Allergies: What You Need to Know
• CDC — Clinical Features of Penicillin Allergy
• National Heart, Lung, and Blood Institute — Asthma
• National Institute of Arthritis and Musculoskeletal and Skin Diseases — Atopic Dermatitis
• EPA — Asthma Triggers: Gain Control

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.