An allergy is an overreaction of the immune system to a substance that is harmless to most people, such as pollen, dust mite, animal dander, a food, insect venom or a medicine. In the classic type the body makes IgE antibodies to the allergen, and contact releases histamine within minutes. Allergy shows up as hay fever, asthma, eczema, hives, food allergy or, at its most severe, anaphylaxis.
Intolerance is not the same thing. Lactose intolerance or headaches after wine do not involve the immune system and are not dangerous. A positive allergy test also does not by itself mean allergy: it shows sensitisation, which matters only when it matches real symptoms on exposure.
Symptoms
- Sneezing, an itchy, runny or blocked nose, and itchy watery eyes
- Wheeze, cough or chest tightness
- Raised itchy welts (hives) and swelling of lips, eyelids or face
- Itching or tingling in the mouth after certain raw fruits or nuts
- Vomiting, cramps or diarrhoea soon after a food
- Flares of eczema
- A rash or swelling after a medicine or an insect sting
- Anaphylaxis: throat tightness, difficulty breathing, faintness or collapse
Causes and risk factors
The tendency to make IgE, called atopy, is inherited. Common inhaled allergens are grass, tree and weed pollens, house dust mite, cat and dog dander and moulds. Foods responsible for most reactions are peanut, tree nuts, milk, egg, wheat, soy, sesame, fish and shellfish. Bee and wasp venom, latex, and medicines, particularly penicillins and anti-inflammatory painkillers, are other triggers. Pollen-food syndrome arises when pollen antibodies cross-react with similar proteins in fruit. Contact allergy to nickel, fragrance or hair dye is a slower, T-cell reaction producing eczema 1 to 3 days after contact.
How it is diagnosed
- Allergy-focused history: What you were exposed to, how quickly symptoms came, and whether it happens every time. It determines which tests are meaningful.
- Skin prick tests: Drops of allergen are pricked into the forearm and read at 15 minutes. Antihistamines must be stopped several days before.
- Specific IgE blood tests: Useful when skin testing is not possible. Component tests can separate serious peanut allergy from mild pollen cross-reaction.
- Patch tests: Allergens taped to the back for 48 hours and read over several days, for contact dermatitis.
- Supervised challenge: Gradually increasing doses of a food or drug in hospital. The definitive way to confirm or rule out an allergy.
- Lung function: Spirometry when asthma may be part of the picture.
Treatment options
- Avoidance: Practical, targeted steps once the trigger is confirmed, and careful label reading for food allergy.
- Antihistamines: Non-sedating tablets for hay fever and hives.
- Steroid nasal sprays and eye drops: The most effective treatment for persistent nasal allergy, used regularly.
- Adrenaline auto-injector: Carried at all times by anyone at risk of anaphylaxis, with training and a written emergency plan.
- Allergen immunotherapy: Injections or under-the-tongue tablets for pollen, dust mite or venom allergy over 3 years. It changes the immune response and the benefit lasts.
- Biologic medicines: Omalizumab for chronic hives, severe allergic asthma and, in some countries, food allergy; dupilumab for severe eczema.
- Drug desensitisation: A hospital procedure when an essential medicine has no alternative.
When it is urgent
Anaphylaxis is life-threatening. If there is throat or tongue swelling, difficulty breathing, wheeze, faintness or collapse after a food, sting or medicine, use an adrenaline auto-injector immediately if one is available, lie down with legs raised, and call local emergency services. A second dose can be given after 5 minutes. Go to hospital even if symptoms improve.
Travelling to Türkiye for treatment
Allergy testing fits a short visit: consultation, skin prick tests, blood tests and lung function can be done in 1 or 2 days, and patch testing needs about 5 days for the readings. Immunotherapy does not fit, since it runs for 3 years with regular doses and should be started where it will be continued. Food and drug challenges carry a risk of reaction and are better done where your follow-up is. If you travel with a serious allergy, carry two auto-injectors and a doctor's letter, and tell the airline in advance.
Send your reports, scans and a short history and a Clinic-Y coordinator replies within 24 hours with suitable teams and written, all-inclusive proposals side by side. Reviewing your case is free.
Frequently Asked Questions
Are large food intolerance panels useful?
IgG food panels and hair or kinesiology tests are not validated and lead to unnecessary diets. Only IgE-based tests interpreted with your history are meaningful.
Can allergies start in adulthood?
Yes. Hay fever, shellfish allergy and drug allergy often first appear in adults.
Can children outgrow food allergy?
Most outgrow milk, egg, wheat and soy allergy. Peanut, tree nut and fish allergy persist in most.
Am I really allergic to penicillin?
About nine in ten people with that label are not when tested. Formal testing is worthwhile because it widens your antibiotic options.