Allergies affect an estimated 40 to 50 million people in the US. And what’s at the root of them all? A trigger allergen. This is a normally harmless substance your immune system reacts to as if it was a threat. Your body usually responds by causing annoying symptoms like a runny nose or sneezing. But some allergy types can cause a more serious reaction.
In this article you’ll learn about the common types of allergies. Also names you might meet for groups of triggers that share certain characteristics.
We don’t know exactly why some people have an overactive immune system. But a family history of allergy is an important factor.
A child is more likely to develop an allergy if their parents have one. The risk is 60-80% if both parents have an allergy and 30-50% if one parent is affected. A child in a family without allergies has a 12% chance of having allergic reactions.
The first step in developing an allergy is sensitization. It might surprise you but you’re unlikely to have an allergic reaction the first time you meet an allergen. Your immune system registers that trigger and arms itself with tailor-made IgE antibodies. Now it’s ready to fight back against the imagined threat at the next encounter.
But not everyone who is sensitized with IgE antibodies will experience allergic reactions. Why? Researchers aren’t sure. What is known is that having an allergy means you are both sensitized and allergic.
The symptoms may feel different but the following allergy types work in the same way. Your immune system detects the allergen again and the antibodies trigger a series of defensive measures. You may feel it in your nose, sinuses, throat, ears, lungs, stomach or on your skin.
Allergic reactions are what’s known as an inflammatory response. Histamine and other fluids, plus white blood cells, can cause swelling and specific symptoms for different allergy types. The rush of mucus is to flush the substance out of your nose. Itching makes you scratch the substance off your skin. The aim is to remove the allergen ASAP.
Pollen is the dusty powder that plants release to reproduce. The types of plants that cause pollen allergies include grass, weeds and trees. When you get allergy symptoms it's called allergic rhinitis, also known as hay fever. Pollen allergy symptoms may include nasal allergies, a cough and sometimes difficulty breathing (chest tightness).
Outdoors you’ll find pollen everywhere. It’s been recorded 400 miles out at sea and two miles high in the atmosphere. Plants release millions of the tiny grains daily. Now climate change is lengthening the season for some species and making their pollen more allergenic. And pollen levels are rising in cities because of pollution.
A misconception about pet allergies is that you’re allergic to animal hair. It’s actually the allergens trapped in fur and feathers. Pets also shed tiny particles of dead skin, a bit like dandruff. This pet dander can cause allergic reactions. The proteins in saliva, sebum and urine can be responsible too.
The most common pets behind animal allergies include cats and dogs. But many other animals can cause them too. Anything producing dander is a possible trigger, regardless of whether it has fur or feathers. Allergic symptoms tend to affect the nose and eyes.
Dust mites live in our homes and indoor public places. They thrive where it’s warm and humid and are commonly found on mattresses, pillows and bed linen and in carpets. Dust mites are different from bed bugs in that they don't bite. Instead they like to snack on our shed skin. They’re also microscopic.
Dust mite allergy is an allergic reaction to their feces and dead skin. Dust mites produce roughly 200 times their weight in waste over the course of their lifetime. These particles are roughly the same size as a pollen grain. So they’re easy to breathe in without realizing. One of the main symptoms of dust mite allergy is a stuffy nose.
Mold is a fungus that breaks down dead organic matter indoors and outside. Microscopic spores float through the air as part of mold’s fertilization process. But they can also end up in your nose.
Around 100 types cause mold allergy. You might get cold-like symptoms, eye allergies, skin reactions or breathing difficulties. Occasionally mold can trigger serious allergic conditions in people exposed to high levels of the allergen at work.
Some people are allergic to insect stings like those from a bee or wasp. A local reaction to the venom may spread beyond the normal wheal or raised bump. For instance your whole arm could be swollen and red, possibly for a few days.
An insect sting allergy can also affect your whole body. This serious reaction can be life-threatening and should be treated as a medical emergency.
It’s possible to be allergic to anything edible. The most common food allergies include peanuts and tree nuts, sesame seeds, cow’s milk, eggs, fish, shellfish and soybeans. You can develop a food allergy at any age but younger children tend to be most affected.
Symptoms range from mild to very severe and may include tingling in your mouth or throat or an itchy rash (hives). Food allergies are different from food intolerances. The first involves your immune system and can be life threatening. The second is difficulty digesting certain foods.
Latex is a natural protein from the sap of the rubber tree. It’s made into things like balloons, rubber gloves, condoms and sneakers.
Some people get allergic reactions when they come into contact with latex. It can cause swelling, itching and skin redness. Also respiratory symptoms if you breathe in particles of latex. Latex allergy can occasionally trigger a severe allergic reaction (anaphylaxis). It should be treated as a medical emergency.
Many reactions to medication are not because of a true drug allergy but may be known side effects. Drug allergies are relatively uncommon; penicillin is probably the best known. They involve your immune system in the same way the other allergy types do. The difference is that even a mild allergic reaction to drugs affects your whole body. You may get hives or even anaphylaxis. The latter is an emergency and you should seek immediate medical attention.
There were four types when British immunologists Robin Coombs and Philip Gell rewrote the allergy textbooks in the early 1960s. They classified allergic reactions into Type I, II, III and IV hypersensitivity. Some scientists now think there may be a Type V.
Each type works differently. This article is mainly about Type I hypersensitivity (also called IgE-mediated allergy). It’s the most common and best understood. Type IV hypersensitivity is common too. It involves T cells, a type of white blood cell and also part of the immune system. The allergic reaction tends to show itself more slowly than the others. That is 48 to 72 hours after exposure to the allergen instead of within 24 hours. The skin allergy contact dermatitis is Type IV.
As well as trigger and classification, there are terms for allergy types with something in common. It could be how you’re exposed to the allergen; what time of year allergic reactions tend to happen; or where on your body you get symptoms. Or about the scale of the reaction.
Environmental allergies are anything that trigger allergic reactions from your surroundings, indoors or outside. For instance, pollen, dust mites, cockroaches, pets and mold. What these allergy types have in common is that the particles are so tiny you won’t know they’re there until you start sneezing.
These are reactions to airborne allergens you breathe in. The list of possible triggers is the same as for environmental allergies, except that latex is on there too. Being in a room with gloves or balloons may put particles of latex into the air. Respiratory allergy symptoms include hay fever and perennial allergic rhinitis. Also shortness of breath, a tight chest and wheezing.
If you get allergy symptoms at certain times of the year, that’s a seasonal allergy. The symptoms are known as seasonal allergic rhinitis. Depending on where you live and what you’re allergic to, it may start in spring and last through to summer or even fall. Common triggers include pollen (tree, grass, weed) and mold. There are seasonal irritants too. Chlorine and wood smoke may make allergy symptoms worse.
The skin is the largest organ of your body. Allergic reactions affect it in different ways that usually make you itch. Touching allergens like nickel (in mobile phones, for instance), hair dye or a particular plant can trigger local reactions such as allergic contact dermatitis (eczema).
Skin allergies can also be a systemic reaction. That is, the outward sign that you’ve breathed in, eaten or injected something your immune system didn’t like. Atopic dermatitis is linked to allergy types like dust mites, pollen and pets. Food, drug allergy and insect stings can cause hives and swelling.
Everyone reacts differently to their trigger. If you're at greater risk of a life-threatening allergic response (anaphylaxis), your allergies may be described as severe. Certain foods, insect stings, latex and medicine are more common causes of severe reactions.
An anaphylactic reaction is usually sudden and normally affects more than one part of your body at the same time. It is a medical emergency that must be treated right away. You may be advised by your healthcare provider to carry epinephrine auto-injectors everywhere you go.
Speak to your healthcare provider If you’re in doubt about what type of allergy you have. They may suggest a skin test or blood tests to help make a diagnosis. A food or drug challenge may be necessary if other test results for those allergy types are inconclusive.
Once diagnosed you’ll be able to discuss treatment options with your healthcare provider. This may include antihistamines, corticosteroids and decongestants. If your symptoms remain they may suggest allergy immunotherapy in the form of allergy shots or tablets. This is the only treatment to tackle the root cause of your allergy. It is not available yet for all triggers.