Allergy Tests: Types, Procedures, and What to Expect

What is an allergy test?

An allergy test is a medical procedure to find out which substances—called allergens—are causing you an allergic reaction. These tests help identify the triggers that cause allergic symptoms such as sneezing, itching, rashes, or more severe reactions in a controlled setting. 

By pinpointing the exact allergens, your healthcare professional can recommend suitable allergy treatment plans or other strategies to help you manage your allergies more effectively.

What are the different types of allergy tests?

There are several types of allergy tests, from blood tests to allergy skin tests. Each test aims to identify various types of allergic reactions:

• Blood test (specific IgE test):

  • The procedure involves taking a blood sample to be sent to a lab. The lab then measures the presence and levels of immunoglobulin E (IgE), produced in response to the addition of specific allergens. 

  • IgE is an antibody involved in allergies. It's useful for people who cannot undergo skin testing due to skin conditions or certain medications.

• Skin prick test, also known as 'scratch test':

  • This is an allergy skin test. Your doctor will place a small amount of allergen on your skin, usually on the forearm or back, and the skin is gently pricked using a thin needle. 

  • If you're allergic, you'll develop a small, itchy bump at the site. This test is quick and can check for multiple allergens at once.

• Intradermal skin test:

  • A small amount of allergen is injected just under the outer layer of skin. This test is more sensitive than the skin prick test and is often used for detecting allergies to things like insect venom or penicillin. 

  • Usually, this is done when the skin prick test results provide a false negative or are inconclusive.

• Patch test:

  • This is another type of allergy skin test that provides you exposure to allergens. Your healthcare provider will place drops of an allergen onto your skin and cover the area with a bandage for 24–72 hours. 

  • Afterwards, they will remove the bandage and check your skin for rashes or any response to allergens. This test helps diagnose contact dermatitis

• Oral challenge test:

  • Under close medical supervision, you consume small amounts of a suspected food allergen to see if a reaction occurs. 

  • An allergy specialist usually performs this test. This test is mainly used for common food allergies when other tests are inconclusive.

When will I need an allergy test?

Your healthcare provider may recommend an allergy test if you experience persistent symptoms such as sneezing, runny nose, skin rashes, hives, coughing, wheezing, or digestive problems that do not improve with standard treatments.

If your symptoms interfere with your daily life or you have a history of severe allergic reactions (anaphylaxis), your healthcare provider may also recommend allergy testing.

Anaphylaxis is a potentially life-threatening problem that can cause hives or swelling, breathing difficulty and a sharp drop in blood pressure that bring on anaphylactic shock. Your health history will determine the cause of a severe reaction and what type of allergy test you should get.

What are some symptoms of allergies?

Different allergies often have different symptoms. For example, food allergies may cause swelling of the lips, whereas allergies to pollen may cause allergic rhinitis, which may cause itchy eyes or nasal congestion. However, consider getting an allergy test if you experience:

• Skin symptoms such as hives, swelling of the face, lips or tongue, or itching.

• Respiratory symptoms like coughing, wheezing, shortness of breath, and chest or throat tightness.

• Nausea, vomiting, abdominal pain, cramps, and diarrhoea.

• Cardiovascular symptoms such as pale skin, weak pulse, dizziness or lightheadedness.

• Burning sensation on your skin or blisters.

• Skin rash or itchy skin.

If you experience any of the above symptoms, don’t hesitate to request an appointment with Thomson Medical. Our doctors will help you to answer any questions you have and provide you with tailored recommendations.

How should I prepare for an allergy test?

1. Stop taking antihistamines at least 3 to 7 days before the test, as they can interfere with results. However, you can continue taking asthma medications if you need them.

2. Consult your doctor if you need to pause any other medications.

3. Avoid alcohol and caffeine on the day of the test.

4. Wear loose, comfortable clothing, ideally with short sleeves for quick access to your arms if you are taking the blood test.

5. Avoid strenuous exercise before the test.

Your healthcare provider will advise you of any other necessary preparations.

What should I expect during an allergy test?

Most allergy tests are quick and relatively painless. The purpose of skin tests is to see how your body responds to allergens. For skin tests, the area will be cleaned and marked, and small amounts of allergens will be applied.

If you have an allergic reaction, you'll develop mild allergies at the site of the scratch or prick, such as itchy skin, watery eyes and congestion. These symptoms usually subside quickly, within one to two hours after the test, however the redness or bumps may remain for several hours. Blood allergy tests involve a simple blood draw. For oral challenge tests, you will be closely monitored for any reactions.

How long does the allergy test take?

It depends on what allergen your provider is testing you for and the type of test. Here's what you can expect:

• An allergy blood test can take 10 minutes because it only involves giving a blood sample.

• A skin prick test can take three to five minutes per allergen, plus the 15 to 20 minutes you wait to see if a reaction occurs.

• A patch test can also be about three to five minutes per allergen. After the patch test is applied, you go home and return a few days later for your provider to check for a reaction.

• An oral challenge test could take three or four hours.

How do I interpret my results?

Allergy test results can be complex. For blood tests, results are given as values that indicate the likelihood of an allergy:

• Values under 0.35: Unlikely sensitisation

• 0.35–0.69: Doubtful significance

• 0.70–3.49: Possible allergy

• 3.50–17.49: Greater possibility

• 17.50–49.99: Very likely

• 50.00–100.00: Very high likelihood

• Over 100.00: Extremely likely

Skin tests are interpreted by the size of the reaction (wheal and redness) at the test site. Always discuss your results with a qualified allergist, as false positives and negatives can occur, and interpretation should consider your medical history.

Are there any risks to an allergy test?

Allergy tests are generally safe, but mild side effects such as itching, redness, or swelling at the test site are common. If you have a reaction to a patch test once you're home, don't apply anything to your skin. Your skin may start to itch under the patch.

Ask your healthcare provider what to do if you begin experiencing intense itching or burning while wearing an allergy patch.

Rarely, more severe reactions to allergy testing may occur, such as an anaphylactic reaction, particularly during intradermal or oral challenge tests, but medical supervision is in place and emergency treatments are available.

How much does an allergy test cost in Singapore?

The cost of allergy testing in Singapore varies depending on the type of test and clinic. For example:

• Skin prick or blood tests:

  • Prices typically start from around SGD 150–300 per allergen panel.

• Comprehensive food or environmental panels:

  • These can cost more, depending on the number of allergens tested.

  • Additional consultation fees may apply.

Always check with your chosen clinic for specific pricing and packages.

FAQs

How do you get tested for allergies?

You can get tested by visiting a healthcare provider or allergist, who will review your symptoms and medical history before recommending the most suitable test, such as a skin prick, blood, patch, or oral challenge test.

What 8 foods are causing 90% of allergies?

The "Big 8" foods responsible for most food allergies are:

1. Milk

2. Eggs

3. Wheat

4. Soybean

5. Peanut

6. Tree nuts

7. Fish

8. Crustacean shellfish

Are allergy tests worth it?

Yes, allergy tests can significantly improve your quality of life by identifying triggers, helping prevent severe reactions, and guiding effective treatment plans.

What triggers allergies?

Common triggers include pollen, dust mites, pet dander, mould, certain foods, insect stings, and medications. Environmental factors and genetics also play a role.

What are the 7 common allergy symptoms?

1. Sneezing

2. Runny or stuffy nose

3. Itchy or watery eyes

4. Skin rashes or hives

5. Coughing or wheezing

6. Swelling (especially lips, tongue, or face)

7. Digestive issues (nausea, vomiting, diarrhoea)

How to make allergies go away?

While allergies cannot usually be cured, symptoms can be managed by avoiding triggers, taking prescribed medications, and, in some cases, undergoing immunotherapy to reduce sensitivity over time.

Does having allergies mean your immune system is weak?

No, allergies are not a sign of a weak immune system. Instead, they result from an overactive immune response to harmless substances.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.