Allergies
Symptoms, Causes & Treatment
Allergic conditions affect over 20% of the UK population. From hay fever and urticaria to anaphylaxis, accurate allergen identification and targeted management significantly improve quality of life and safety. Allergen immunotherapy is the only treatment that modifies the underlying allergic disease.
What are Allergic Conditions?
Allergic conditions encompass a spectrum from mild hay fever and urticaria to life-threatening anaphylaxis. They share the common mechanism of IgE-mediated immune sensitisation to specific allergens. Common allergic conditions include allergic rhinitis, food allergy, drug allergy, venom allergy, urticaria, and eczema. Accurate diagnosis guides safe allergen avoidance, pharmacological management, and allergen immunotherapy.
Symptoms of Allergic Conditions
Allergic symptoms range from mild nasal congestion to life-threatening anaphylaxis. The speed of onset, severity, and pattern of symptoms guide urgency and treatment.
Sneezing, nasal congestion, and rhinorrhoea · Itchy, watery, or red eyes (allergic conjunctivitis) · Urticaria (hives) and angioedema · Eczematous skin flares triggered by allergen exposure · Occupational symptoms improving on days off work · Symptoms seasonal or perennial
Sudden throat swelling, difficulty breathing, or speaking · Rapid onset urticaria with hypotension and collapse · Severe bronchospasm after allergen exposure — this is anaphylaxis. Call 999 immediately. Use adrenaline auto-injector (EpiPen) if available.
Sudden throat swelling, difficulty breathing, severe urticaria, hypotension, or collapse after allergen exposure — this is anaphylaxis. Call 999 immediately. Use EpiPen IM into the outer thigh. This is a medical emergency.
What Causes Allergies?
Allergic conditions arise from IgE-mediated immune responses to specific allergens. Understanding the allergen and reaction type guides safe and effective management.
Allergic rhinitis (hay fever) is caused by IgE-mediated sensitisation to inhaled allergens including grass pollen, tree pollen, house dust mite, and animal dander. It is the most common allergic condition in the UK, affecting 20% of the population.
Food allergy is an IgE-mediated immune reaction to specific food proteins, causing symptoms within minutes of ingestion. The 14 major allergens include peanuts, tree nuts, milk, eggs, wheat, fish, shellfish, sesame, soya, celery, mustard, sulphites, lupin, and molluscs.
Urticaria (hives) causes itchy wheals that migrate over the skin. Acute urticaria (less than 6 weeks) is usually triggered by infection, medication (NSAIDs, penicillin), or food. Chronic spontaneous urticaria (more than 6 weeks) is often autoimmune and treated with antihistamines and omalizumab.
Drug allergy encompasses IgE-mediated reactions (penicillin, NSAIDs, aspirin) and non-immune hypersensitivity reactions. Up to 95% of patients labelled penicillin-allergic can safely receive it after formal allergy assessment. Mislabelling penicillin allergy increases antibiotic resistance and infection risk.
Anaphylaxis is a life-threatening systemic allergic reaction caused by massive mast cell degranulation. Triggers include food, medications (NSAIDs, antibiotics, contrast), insect stings, and latex. Adrenaline IM 0.5mg is the first-line emergency treatment. EpiPen is the auto-injector for community use.
Venom allergy (bee and wasp stings) causes anaphylaxis in 1–3% of the population. Patients with confirmed venom anaphylaxis should carry an EpiPen and be referred for venom immunotherapy, which is 90–95% protective against future stings.
Key Risk Factors
Diagnosing Allergies
Skin prick testing and specific IgE blood tests identify allergen sensitisation. Tryptase confirms anaphylaxis. Oral food challenges provide definitive food allergy diagnosis in specialist allergy clinics.
Treatment for Allergic Conditions
Allergy management uses a combination of allergen avoidance, pharmacological control, emergency preparedness, and allergen immunotherapy. Treatment is tailored to the specific allergen and reaction type.
Supportive Measures
Carry two EpiPens at all times if prescribed. Wear a MedicAlert bracelet. Inform all food handlers of food allergies. Take antihistamines at the first sign of allergic reaction. Use intranasal steroids consistently during the allergy season. Avoid known allergens. Have a written allergy action plan.
Long-Term Allergy Management
Allergic rhinitis and asthma require long-term pharmacological management and consideration of allergen immunotherapy. Food and drug allergies require ongoing allergen avoidance and emergency planning. Annual allergy clinic review ensures treatment remains optimal and safe.
When to Seek Help
Sudden throat swelling, difficulty breathing, severe urticaria with hypotension or collapse — this is anaphylaxis. Call 999 immediately. Administer EpiPen IM into the outer thigh. Lie flat with legs raised unless breathing difficulty prevents this.
See a GP for new allergic symptoms, uncontrolled hay fever, urticaria, or to discuss EpiPen prescription after any systemic allergic reaction. An online consultation is appropriate for non-emergency allergy management and prescription review.
Staying Safe with Allergies
Allergy management focuses on allergen avoidance, emergency preparedness, and where appropriate, allergen immunotherapy to reduce long-term sensitisation.
Carry an adrenaline auto-injector (EpiPen) at all times if prescribed. Keep two available. Replace before expiry. Ensure family, friends, and colleagues know how to use it. Register with your school or workplace as an adrenaline auto-injector user.
Read food labels carefully and always ask about allergen content when eating out. Inform restaurants and food businesses of your allergen. Use the CellaVision or Allergy Translations app when travelling abroad to communicate your allergy in other languages.
Take daily non-sedating antihistamines during the pollen season (April–September in the UK) to prevent hay fever symptoms. Starting 2 weeks before the season begins provides better control than reactive treatment.
Ask your GP about allergen immunotherapy (desensitisation) if allergy significantly impacts quality of life despite medication. SLIT tablets for grass pollen and house dust mite are NICE-approved and reduce symptoms by 30–40% over 3 years of treatment.
Avoid known drug allergens and ensure your GP record and hospital records clearly document your drug allergy with the reaction type. Carry a drug allergy card. Request formal drug allergy assessment if the label is uncertain — most ‘penicillin-allergic’ patients can safely receive it.
Wear a medical alert bracelet or necklace if you carry an EpiPen. This ensures emergency responders are aware of your allergy even if you are unable to communicate. Register with a medical alert service (MedicAlert, SOS Talisman).
Getting Treatment for Allergies
A GP can prescribe intranasal steroids and antihistamines for allergic rhinitis, prescribe and review adrenaline auto-injectors, and refer to NHS allergy clinics. Online consultations are appropriate for hay fever and urticaria management. Anaphylaxis requires in-person emergency assessment.
Expert clinical advice, when you need it.
Allergies — Frequently Asked Questions
Allergy develops when the immune system produces IgE antibodies against harmless substances (allergens). On re-exposure, allergen-specific IgE triggers mast cell degranulation, releasing histamine and inflammatory mediators causing sneezing, itching, swelling, and in severe cases, anaphylaxis.
Anaphylaxis causes sudden throat swelling, difficulty breathing, severe urticaria, blood pressure drop, and collapse, typically within minutes of allergen exposure. Call 999 immediately. Use adrenaline auto-injector (EpiPen) if available. Lie flat with legs raised unless breathing is difficult.
The most effective treatment is a daily intranasal corticosteroid spray (fluticasone, mometasone) — start 2 weeks before the season. Non-sedating antihistamines help with sneezing and itch. Allergen immunotherapy is the only disease-modifying treatment that reduces long-term hay fever symptoms.
Skin prick testing and specific IgE blood tests identify allergen sensitisation. A positive test confirms sensitisation but must be interpreted alongside symptoms — sensitisation without symptoms does not require treatment. Oral food challenges are the gold standard for food allergy diagnosis.
Allergen immunotherapy gradually desensitises the immune system to specific allergens over 3–5 years. SLIT tablets for grass pollen and house dust mite are NICE-approved, reducing symptoms by 30–40% long-term. Venom immunotherapy provides 90–95% protection against future anaphylaxis from bee and wasp stings.
Up to 95% of patients labelled penicillin-allergic can safely tolerate penicillin after formal allergy assessment. Most labels arise from intolerance reactions misidentified as allergy. Mislabelling drives broader antibiotic use, promoting resistance. Request formal allergy assessment if your label is uncertain.
Avoid all forms of the food. Carry two EpiPens at all times. Wear a medical alert bracelet. Inform all food handlers. Have a written allergy action plan. Consider referral for oral immunotherapy (OIT) for peanut allergy in children aged 4–17, now available at NHS allergy centres.
A GP can arrange allergy testing referral, prescribe intranasal steroids and antihistamines for rhinitis, prescribe and review adrenaline auto-injectors, and refer to an NHS allergy clinic. Online consultation is appropriate for hay fever and mild allergic conditions. Anaphylaxis requires in-person emergency assessment.