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Food allergy symptoms can be immediate — usually within minutes to two hours — such as a raised itchy rash (hives), swelling of the lips or face, vomiting, or a runny nose, or delayed over several hours to days, such as worsening eczema, reflux, diarrhoea, or blood or mucus in the stool. Swelling of the tongue or throat, difficulty breathing, a hoarse cry, or floppiness are signs of a severe reaction (anaphylaxis) — call 999 immediately.
Key takeaways
- Immediate reactions usually appear within minutes to two hours of eating the food.
- Delayed reactions can take hours to days and often affect the skin and gut.
- An allergy involves the immune system; an intolerance does not and is rarely dangerous.
- Swelling of the tongue or throat or any difficulty breathing is an emergency — call 999.
Immediate (fast) reactions
Most obvious allergic reactions happen quickly — within minutes and up to about two hours of eating the food. Common signs include a raised, itchy rash (hives or welts), swelling of the lips, face, or eyes, an itchy or tingly mouth, sudden vomiting, a runny or blocked nose, and sneezing. These are the reactions most parents picture, and they are usually easy to link to the food just eaten.
Delayed reactions
Not all food allergies are fast. Delayed (non-IgE) reactions can build over several hours to a couple of days and tend to affect the skin and gut: worsening eczema, persistent reflux or vomiting, diarrhoea or constipation, tummy pain, and sometimes blood or mucus in the nappy. Because they are slower, they are harder to connect to a specific food — which is where keeping a feeding and symptom log really helps.
Allergy or intolerance?
An allergy involves the immune system and can affect the skin, gut, and breathing. An intolerance — such as difficulty digesting lactose — does not involve the immune system, mainly causes digestive discomfort, and is not life-threatening. The two are often confused, but the distinction matters, so it is worth getting a professional assessment rather than self-diagnosing.
Emergency signs — call 999
A severe reaction (anaphylaxis) is a medical emergency. Call 999 immediately if your baby or toddler has swelling of the tongue or throat, difficulty or noisy breathing, a hoarse cry or cough, sudden tiredness, floppiness, or pale or blue skin. Tell the operator you think it is a serious allergic reaction.
What to do for a milder reaction
For a mild reaction such as a few hives or a runny nose, stop offering the food and contact your GP, who can arrange an assessment or referral. Note what your child ate, how much, how soon symptoms appeared, and what you saw — a clear record makes diagnosis far easier. VitaBaby lets you log the food and a symptom note together so the timeline is captured while it is fresh.
FAQ
My baby got a rash around his mouth after eating egg — is it an allergy?
A raised, itchy rash or hives soon after a new food can be an allergic reaction; redness only where food touched the skin is often just irritation. Stop the food, note the timing and symptoms, and speak to your GP. If there is any swelling of the tongue or throat or trouble breathing, call 999.
How soon do food allergy symptoms appear in babies?
Immediate reactions usually appear within minutes to about two hours. Delayed reactions can take several hours to a couple of days and tend to show as eczema, reflux, or tummy and nappy changes.
Is it a food allergy or just an intolerance?
An allergy involves the immune system and can affect skin, gut, and breathing; an intolerance does not involve the immune system, mainly causes digestive discomfort, and is not dangerous. A GP can help tell them apart — avoid self-diagnosing.
When is an allergic reaction an emergency?
Call 999 immediately if there is swelling of the tongue or throat, difficulty or noisy breathing, a hoarse cry, floppiness, or pale or blue skin. These are signs of anaphylaxis.
Sources
- Food allergy — Symptoms — NHS
- Anaphylaxis — NHS
- Food allergy in children — Allergy UK