How Are Allergies Diagnosed?

A healthcare provider will test for allergies by asking questions about your symptoms and medical history. They will then use tests and procedures to find what triggers the allergy. Allergy tests include skin prick tests, puncture or intradermal tests, and blood tests to check for increased levels of IgE-allergy antibodies. 

An allergist immunologist is a healthcare provider who specializes in diagnosing and treating allergies and primary immune disorders. With their help, you can get answers and access treatments that can improve your quality of life if you have allergies.

Medical History

The first step to diagnosis is gathering information. A healthcare provider will ask questions about your personal and family medical history. Allergies can commonly co-occur with other conditions (e.g., asthma) and are more likely if your family members also have them.

The healthcare provider will also ask about other triggers that may have caused symptoms. They need to understand if you have been exposed to any allergens recently. This helps narrow down possible triggers and put together a focused treatment plan. The healthcare provider will also consider other factors, such as your age, your occupation, and the severity of symptoms.

Physical Exam

Healthcare providers use physical exams to help diagnose allergies. They look for symptoms, such as redness, swelling, rashes, and itchy bumps, all of which can indicate allergies.

The healthcare provider will also listen to your lungs and look inside your nose and throat to check for respiratory or nasal symptoms. They can then use allergy tests to help confirm a diagnosis once they better understand what is going on.  

Allergen Testing

Allergy skin testing is a common way to find out if you have allergies. Allergists use this test to figure out whether you are allergic to something. 

Skin tests are a type of exposure test in which an allergist puts a very small amount of many different allergens on your skin. They will then see how your body reacts. You may have a reaction to one or more of the tested substances if you have an allergy. The allergen may cause a wheal (a type of bump) and redness to appear on your skin. The area around the wheal might be itchy. 

Skin tests help pinpoint what allergens cause a reaction. Skin tests can include:

• Skin prick testing (SPT): An allergist places a drop of an allergen on your forearm or back using a small probe or tiny needle to scratch the same area.
• Intradermal injection testing: An allergist may also perform intradermal testing if SPT is negative and your history is still concerning for a significant environmental allergy. They will inject a small amount of allergen under your skin, usually on your forearm.
• Patch tests: This type of testing is a way to look for triggers for allergic contact dermatitis. The allergen is taped onto your skin for 48 hours. Initial readings are done when the tape is removed. Final readings to see what you are sensitive to are usually done 48 hours after that.

Skin testing is a way for healthcare providers to learn what trigger your allergies. This helps them give suggestions about how to avoid the things that will cause problems and provide proper treatment.

Blood Tests

Allergists use allergen-specific immunoglobulin E (IgE) blood tests to help diagnose allergies. These blood tests measure the concentration of IgE antibodies made to specific allergens in your blood.

IgE blood tests can test for many types of allergies by trigger, such as pollens, mold, food, or animal dander. IgE is a protein created by the immune system to fight off allergens. It's likely you have an allergy if high levels of IgE are detected against specific allergens.

Healthcare providers sometimes combine an IgE blood test with skin prick tests to diagnose allergies more accurately. The results can then be used to determine what allergens are causing reactions and if medication or therapies can help.

Other Testing

Healthcare providers might use other types of tests to help diagnose allergies. These include spirometry and challenge tests.

Spirometry

Spirometry detects signs of lower airway restriction or obstruction. A healthcare provider may use this test if you are experiencing symptoms like coughing, wheezing, and shortness of breath.

Spirometry measures how much air you can breathe out, as well as how quickly you can do it. People with allergies often have tighter and more obstructed lungs. This makes it harder for them to take deep breaths and exhale a lot of air.

Allergists can screen for co-existing asthma by testing the amount and speed of breath. Asthma and chronic obstructive pulmonary disease (COPD), which often occur alongside allergies, can be detected with spirometry. The results can guide treatment plans for people with allergies.

Challenge Tests

Provocation testing is more commonly known as challenge testing. An allergist can use this test to figure out what's causing your allergic reactions. They do this by slowly giving you a tiny bit of allergen at a time during a supervised visit. The allergist will monitor you to see if you have any kind of reaction and, if so, how severe it is. 

Challenge testing, or oral food challenge, is often used to help diagnosis of a food allergy. It's considered the gold standard test for food allergies.

An allergist will usually order allergy tests, depending on your history, and review these with you before any challenge testing. They will supervise challenges in a location where anaphylaxis can be treated right away with epinephrine if there's a risk for anaphylaxis. Never try challenges at home when there's a significant risk for anaphylaxis

Screening for Related Conditions

Asthma and COPD often occur alongside allergies. History and spirometry testing help rule out or diagnose these illnesses. 

Eczema (atopic dermatitis) is an inflammatory skin condition that commonly occurs alongside allergies. It is diagnosed with a skin exam. Other, more rare conditions can also mimic allergies. A healthcare provider will discuss what tests might be needed to rule out other conditions and confirm a diagnosis.

A Quick Review

Allergies are usually diagnosed by allergists or immunologists, who use various tests to determine the cause. Common tests used to diagnose allergies include allergen tests and more specialized procedures like spirometry and provocation testing.

It's important to partner with a healthcare provider for diagnosis and individualized care. Allergists can determine the best treatment options for you.