Having multiple allergies

A girl thinking

We’d love to say it’s only possible to be allergic to one thing. Ever. That your body makes its pick and sticks to it. Or at least that you can only have one allergy at a time. But it doesn’t work like that when you’ve got an overactive immune system.

We’ll explain what’s happening when symptoms seem to have more than one trigger. You’ll also find out what treatments are available if you do have multiple allergies.

How do multiple allergies start?

The first step in getting an allergy is sensitization. You breathe in pollen from an unfamiliar plant, pat a dog or eat a food for the first time and it puts your body on full alert. Your immune system has its fists up ready to fight without you even knowing it. It starts producing immunoglobulin E (IgE) antibodies specific to each trigger. The next time you come into contact with that substance you could have an allergic reaction.

Your immune system goes on developing throughout your life as you meet each new threat – real or, as in allergy, something normally harmless. That means you can get new allergies over time.


If you have multiple allergies, you’re not alone. Over half of all people with allergies are sensitized to more than one potential allergen.

Most people with allergy are “polysensitized”

If you have multiple allergies, you’re not alone. Over half of all people with allergies are sensitized to more than one potential allergen.

The medical term is polysensitization. Monosensitized on the other hand means that your body only reacts to one allergen. Poly comes from the ancient Greek and means “many”, while mono means “one”.

Sensitization doesn’t always lead to allergy symptoms though. But it can. And if you have allergy symptoms caused by more than one trigger you are polyallergic. Fancy word for a very annoying condition, right?

Allergy symptom threshold

Allergy is different for everyone, including the amount of allergen it takes to trigger symptoms. You might have several allergies but only experience mild if any symptoms until you meet all your triggers at once.

For example, pollen season could be a tipping point if you’ve got low-level perennial allergies. Maybe your system is pumping out IgE all year because you’re reacting to pet dander, dust mites or mold – but not enough for you to feel affected. Then pollen season hits and the higher allergen levels push your immune system too far. Chemicals such as histamine are released, which cause the sneezing and itching.

Logically you might think you’ve got pollen allergy and still have no idea that year-round exposure to other triggers is contributing to your wretchedness.

A girl sneezing in yellow.

What is hay fever exactly?

Cross-reactions: allergy triggers that trigger each other

It’s possible to react to an allergen you’ve never encountered before because one of its proteins is very similar to one of your triggers. This is called a cross-reaction.

Cross-reactions can happen with different plants. For instance, you could be allergic to alder pollen and get hay fever from birch, beech and oak. And if you react to one grass pollen type then it’s common to be sensitive to others too. Timothy grass, for example, is similar to other common related grasses including: Sweet Vernal, Orchard (Cocksfoot), Perennial Rye, Meadow Fescue, Kentucky Bluegrass (June Grass) and Redtop.

People with respiratory allergies can also have cross-reactions when eating certain foods for the same reason: The protein in the food is very like the allergen. This is called pollen food syndrome or oral allergy syndrome.

For example, if you’re allergic to ragweed pollen, you might get a mild, local reaction in your mouth, throat, lips or face when you eat cantaloupes, honeydew melons, watermelon, banana, cucumber, white potato and zucchini.

If you experience symptoms when eating certain foods you should speak to your health care provider in case you have a more serious food allergy. Such an allergy could cause anaphylaxis and potentially be life-threatening.

Will having more than one allergy make my symptoms worse?

Your immune system is fighting several battles at once so you may find your symptoms are more severe.

Inflammation and other symptoms can be more intense. This can have consequences for other areas of your life. A badly blocked nose makes it hard to get a good night’s sleep and affects how you feel during the day. It may become difficult to concentrate. Symptoms may even contribute to depression and anxiety.

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Will I need a cupboard full of allergy meds?

If you can’t avoid whatever triggers your allergy, medication such as antihistamines and corticosteroids can temporarily help ease your symptoms whether you have one allergy or several. After all, it’s the same immune response.

Antihistamine blocks the histamine causing the inflammation behind your rash, sneezing, coughing, runny nose and watery or itchy eyes. Corticosteroids mimic a natural hormone in your body and are anti-inflammatory too.

Both allergy meds are available in different forms and strengths. Your health care provider can help you find the best one for you. You can also ask your pharmacist for advice on the options available over the counter.

Can I have immunotherapy for multiple allergies?

As mentioned before, when you have multiple allergies they can built on each other and it might become difficult to keep symptoms in check. Antihistamines and corticosteroids may not be enough anymore. That’s where allergy immunotherapy could come in.

Allergy immunotherapy can be a turning point for your allergies. Over months or years regular small doses of an allergen desensitize your body. These doses can be given as injections (you might have heard of “allergy shots”), or tablets under the tongue. The treatment trains your immune system not to react anymore, or at least not so strongly. This can reduce your allergy symptoms and therefore the amount of medication you need.

There are allergy immunotherapy treatments for triggers such as specific pollen types, dust mites, cats or dogs. Your health care provider will find the solution that works best for you.

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How does allergy immunotherapy for multiple allergies work?

There are different options for tackling multiple allergies with immunotherapy. Some treatment routines will target many triggers at the same time. That’s one way to go. Another would be to pick relevant allergens, which is an efficient and well-documented approach.

Cross-reactions between different allergens can be an absolute pain, meaning lots of other triggers make trouble for you too. But there is an upside when it comes to allergy immunotherapy: Target the right allergen and you can solve a bunch of problems at once. That’s the principle of single-allergen immunotherapy.

This approach uses one allergen to reduce the symptoms caused by many. For example, studies have shown that immunotherapy with the pollen from one species of grass is effective in treating people sensitized to several species. This is because these pollens’ molecular structure is similar. So the treatment also desensitizes your body to that type of allergen.

Starting with the allergy causing the most trouble can have a positive impact not only on those particular symptoms but also on the other allergies. Scientists have discovered that immunotherapy for dust mite allergy can help people who also react to pollen. Afterwards you should have fewer symptoms all year round including pollen season, and rely on allergy meds much less.

Don’t guess: take an allergy test

The only way to find out for sure what’s causing your immune system to overreact is with allergy testing. Your health care provider will then be able to tell you which treatment is right for you and help you through the whole process.

An allergy test can help uncover underlying allergies. That way you can reduce your exposure to specific triggers, which could contribute to keeping you under the allergy symptom threshold.

And if allergy immunotherapy is the path for you, your health care provider can use the results to get a clear picture of your trigger profile and put together a treatment plan that’s right for you.

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