How are allergies diagnosed?

1. Medical History

Your doctor will start by taking a detailed medical history, including:

• Your symptoms and their severity


• When and how often the symptoms occur


• Any known triggers or allergens


• Your family history of allergies


• Any other medical conditions you have


• Medications you are currently taking

2. Physical Examination

The doctor will perform a physical examination to look for signs of allergies, such as:

• Skin rashes or hives


• Swelling


• Redness or irritation in the eyes, nose, or throat


• Wheezing or difficulty breathing

3. Allergy Tests

Several tests can help identify specific allergens. Common allergy tests include:

Skin Prick Test (SPT)

During a skin prick test, small amounts of common allergens are applied to the skin, usually on the forearm or back. The skin is then pricked or scratched to allow the allergen to enter. If you are allergic to the substance, a small red bump (wheal) will appear within 15-20 minutes.

• Advantages: Quick results, minimally invasive


• Considerations: May cause mild discomfort, not suitable for people with certain skin conditions or those taking antihistamines

Blood Test

A blood test, such as the ImmunoCAP test or the radioallergosorbent test (RAST), measures the levels of specific IgE antibodies in the blood in response to allergens. This test can identify a wide range of allergens.

• Advantages: Useful for those who cannot undergo skin testing, no risk of an allergic reaction during the test


• Considerations: May take longer to get results, can be more expensive

Patch Test

A patch test is used to diagnose contact dermatitis, a type of skin allergy. Small amounts of potential allergens are applied to patches, which are then placed on your skin. The patches are left on for 48 hours, after which the doctor checks for reactions.

• Advantages: Can identify delayed allergic reactions


• Considerations: Requires multiple visits, results take several days

Elimination Diet

An elimination diet is used to identify food allergies. This involves removing suspected allergens from your diet for a period of time and then gradually reintroducing them while monitoring for symptoms. This should be done under medical supervision.

• Advantages: Can help pinpoint specific food allergies


• Considerations: Requires careful planning and monitoring, not suitable for severe allergies

Challenge Test

In a challenge test, you consume a small amount of the suspected allergen under medical supervision to see if it triggers a reaction. This test is typically done in a controlled environment where immediate medical care is available if needed.

• Advantages: Provides definitive diagnosis


• Considerations: Risk of severe allergic reaction, should only be done under medical supervision

4. Other Diagnostic Methods

Additional diagnostic methods may be used depending on the type of allergy and symptoms, such as:

• Nasal Smear: Examining nasal secretions under a microscope to check for increased levels of eosinophils, a type of white blood cell that indicates an allergic response.


• Chest X-ray or Sinus Imaging: Used to rule out other conditions and check for complications related to allergies.