Oral allergy syndrome (pollen food syndrome) in children

What it is

Some people get an itchy or tingly mouth and throat after eating certain raw fruits, vegetables or nuts. This is oral allergy syndrome, also called pollen food syndrome or pollen food allergy syndrome. The NHS says it’s not usually serious.

It happens because some proteins in these foods look a lot like proteins in tree, grass or weed pollen. In a child who is allergic to pollen, the immune system mistakes the food protein for pollen and reacts (ACAAI). Heat changes the shape of these proteins, so the same food cooked usually causes no symptoms (ACAAI, NHS).

It’s uncommon in babies and toddlers

ACAAI says pollen food allergy syndrome typically doesn’t appear in young children. It’s more common in older children, teens and young adults who have eaten the food for years without problems. That’s because it follows hay fever, which children don’t usually develop until after the toddler years (ACAAI). BSACI, the British allergy society, says it usually affects teenagers and adults but can occur at any age, especially with spring or summer hay fever.

So if your baby has a reaction around the mouth after a new food, oral allergy syndrome isn’t the likely cause. Treat it like any possible food reaction or irritation:

• Redness only where the food touched, from acidic foods like tomato or berries, is often harmless contact irritation: see rash around the mouth.
• A few hives, mild puffiness around the eyes or vomiting once may be a food allergy: stop the food and call your pediatrician or GP before offering it again. Lips, mouth, tongue or throat that suddenly swell, or trouble breathing, are an emergency (see below). See how to introduce allergens.

Signs

The AAAAI and ACAAI describe:

• itching or tingling of the mouth, lips, tongue or throat
• a scratchy throat, sometimes itchy ears
• sometimes a few hives around the mouth

Some people also get swelling of the lips, mouth, tongue or throat (ACAAI). The NHS lists lips, mouth, throat or tongue that suddenly swell as a reason to call 999, so this guide treats sudden swelling as an emergency sign (below), not as a mild one.

Symptoms usually start within minutes of the raw food touching the mouth and settle quickly once it’s swallowed or spat out (ACAAI, Oxford University Hospitals). They usually stay in the mouth. Rarely, they spread further, or cause severe throat swelling and trouble swallowing or breathing (AAAAI, ACAAI).

Common trigger foods

Which foods cause it depends on which pollen a child reacts to. ACAAI lists:

• Birch pollen: apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, plum
• Grass pollen: celery, melons, oranges, peaches, tomato
• Ragweed pollen: banana, cucumber, melons, sunflower seeds, zucchini

The Worcestershire NHS leaflet adds that most people with hay fever have no symptoms from food. If your child eats these foods happily, keep offering them.

Babies usually eat many of these foods cooked anyway. The AAP says that apart from mashed banana, most fruits and vegetables for babies should be cooked until soft, and it lists raw vegetables and fruit chunks, such as apple chunks, as choking hazards under 1. See carrot and apple for safe forms. See the food pages for safe forms of celery, peach, kiwi and pear.

What helps

If your child has been diagnosed with oral allergy syndrome:

• Cooked versions are usually fine. Baking or microwaving breaks down the proteins (AAAAI), and canned fruit may cause fewer symptoms. Roasted nuts can still cause symptoms (Worcestershire NHS).
• Peeling may help, because the protein is often concentrated in the skin (AAAAI).
• Pollen season can make it worse (AAAAI).
• Avoid only the raw foods that have caused symptoms (BSACI). If many foods are involved, ask about a dietitian.
• If symptoms start, stop eating the food, spit it out and rinse the mouth with water (Oxford University Hospitals). Ask your doctor whether an antihistamine is right for your child, and what dose.

Nuts and soy are different

A mouth itch from peanuts or tree nuts may signal a more serious nut allergy (AAAAI). BSACI says anyone with symptoms to tree nuts or peanuts, whether mild, moderate or severe, should be referred to an allergy specialist, along with anyone who has had a severe reaction, or symptoms beyond the mouth, to soy milk or to raw or cooked fruit or vegetables. Don’t assume a reaction to nuts is “just” oral allergy syndrome: see your doctor, and see tree nut allergy and peanut introduction.

When to see a doctor

Talk to your pediatrician or GP if your child keeps getting an itchy mouth from the same raw food (ACAAI suggests seeing an allergist). They’ll ask what happened; for fruit and vegetables only, BSACI says the history alone can often confirm it, without tests. See food allergy testing.

When it’s an emergency

Mouth itch on its own isn’t an emergency. But treat these as anaphylaxis: swelling of the throat or tongue, lips or mouth that suddenly swell, trouble swallowing or breathing, wheezing or a cough that won’t stop, a hoarse voice, turning pale or floppy, or signs in more than one part of the body at once.

If your child has an epinephrine (adrenaline) auto-injector, use it right away, then call for an ambulance. Call 911.Call 999.Call your local emergency number (such as 112 in Europe or 000 in Australia). If you don’t have an auto-injector, call straight away. If you’re alone with your child, use the auto-injector first if they have one, then call on speaker. Don’t leave your child to find a phone. Keep your child lying down, never standing or walking (on their side if they’re vomiting, head and shoulders a little raised if breathing is hard), and go to hospital even if they seem better. See signs of anaphylaxis.

Where US and UK advice differs

• The name. US allergists (ACAAI) call it pollen food allergy syndrome; UK services usually call it pollen food syndrome. Both also use oral allergy syndrome.
• The pollens. ACAAI names birch, grass and ragweed pollen. In the UK, BSACI says it’s mainly tree pollen, mostly birch, but also hazel and alder.
• Tests. ACAAI says diagnosis comes from the history and, in some cases, skin prick tests and food challenges. BSACI says that for reactions only to fruit and vegetables that fit the pattern, tests usually aren’t needed.