Skin Prick Test: How is it done and who is it suitable for?
If you sneeze, itch, or have a runny nose without a clear cause… you might be living with allergies without knowing it. Skin Prick Test is a tool to help find the answer and lead to targeted treatment.
Allergies are a common health problem at all ages, both in children and adults. Many people may have chronic symptoms for years without ever knowing what exactly they are allergic to.
Skin Prick Test is a method doctors use to identify the true allergens in the body to provide the most effective care and treatment.
What is a Skin Prick Test?
Skin Prick Test is a medical test used to identify allergens that cause allergic reactions in the body. The doctor applies extracts of substances that may cause allergies onto the skin, then gently pricks the skin with a small needle to allow the substance to enter the upper layer of the skin. The reaction is then observed.
Examples of allergens tested
| House Dust Mites | Dermatophagoides pteronyssinus, D. farinae are major causes of allergies in Thailand, found in up to 80% of mattresses, pillows, and sofas. They thrive in high humidity. |
| Pollen from Flowers/Grass | Pollen from trees, grass, and weeds that spread in the air seasonally. |
| Pet Hair and Skin Cells | Cats, dogs |
| Mold | Mold spores in the environment and buildings |
| Cockroaches | Proteins from cockroaches, a major cause of urban allergies |
| Food | Milk, eggs, nuts, seafood, wheat flour, sesame, and others (only if suspected) |
| Medications | In some cases, allergy to certain medications can be tested |
Who is the Skin Prick Test suitable for?
The Skin Prick Test is suitable for those who suspect they have allergies, especially those with the following characteristics:
- Have chronic allergy symptoms without a known cause
- Have a family history of allergies
- Frequently sneeze, have a runny nose, nasal congestion, or itchy eyes without fever
- Have asthma or respiratory problems
- Have hives or dermatitis of unknown cause
- Want to plan treatment and avoid allergens correctly
- Considering immunotherapy treatment
- Have not taken antihistamines for at least 7 days before the test
The test can be done from age 2 and above, both children and adults, with the doctor assessing suitability each time.
Groups to be cautious before testing
- Those with severe asthma that is not well controlled
- Those who are pregnant
What allergy symptoms should prompt testing?
These symptoms may seem ordinary, but if repeated or chronic, they may be warning signs from the body indicating it’s time for testing.
| Respiratory System | Skin & Eyes |
| • Repeated sneezing • Clear runny nose / chronic nasal congestion • Chronic cough, wheezing • Shortness of breath, chest tightness |
• Itchy rash, frequent dermatitis on folds, neck • Recurrent hives suspected from food allergy • Red eyes, itchy eyes, watery eyes • Swelling around eyes or lips |
Additionally, if you have symptoms from food such as nausea, diarrhea, or swelling of the mouth or tongue after eating certain foods, you should also get tested to find the true cause.
Advantages of Skin Prick Test
- Quick results within 15–20 minutes, no long wait
- Highly accurate and a standardized test accepted by allergists worldwide
- Can test multiple allergens at once
- Painless, feels like a slight scratch only
- Safe, with doctors monitoring throughout the test, greatly reducing risks
- Helps plan targeted treatment, knowing what to avoid and how to treat effectively
- Cost-effective in the long run compared to buying allergy medications and treating symptoms without knowing the cause
Steps of Skin Prick Test
| Step 1 | Doctor takes medical history and assesses allergy symptoms before testing to select appropriate allergens for each individual |
| Step 2 | Clean the skin area to be tested (usually the inner arm) until dry and clean |
| Step 3 | Drop each allergen extract onto the skin, arranged in rows about 3 cm apart |
| Step 4 | Use a small needle (Lancet) to prick the skin so the extract penetrates |
| Step 5 | Wait 15–20 minutes for the reaction to appear (do not move or scratch the arm) |
| Step 6 | Doctor examines and measures the size of the red swollen area (Wheal) to interpret the test results |
Note: Prepare by avoiding antihistamines for at least 3–7 days and inform the doctor if you are taking any other medications.
How to interpret Skin Prick Test results?
After the test, results can be read within 15–20 minutes. The doctor observes the skin area exposed to the allergens and considers:
- Positive (+): Clear red raised wheal and flare, often with itching, indicating the body reacts to that allergen
- Negative (-): No abnormal skin reaction, indicating no allergy to that allergen
- The doctor measures the wheal size in millimeters to determine the severity of the allergy
The doctor will combine the test results with medical history and physical examination to diagnose and plan appropriate treatment for each individual.
Side effects of Skin Prick Test
Generally, Skin Prick Test is very safe with minimal side effects.
- Common (temporary) symptoms: Itching, mild red raised rash at the test site, usually improving within 30–60 minutes. Nurses will provide initial care by applying soothing cream.
- Less common symptoms: Increased swelling and redness after the test, usually resolving on its own or with topical medication.
- Severe symptoms (very rare): Severe allergic reaction or anaphylaxis may occur very rarely but can be treated immediately as the test is done in a hospital equipped for emergencies.
FAQ: Common questions about Skin Prick Test
Q: Is it necessary to get tested if allergy medications relieve symptoms?
Allergy medications only relieve symptoms temporarily but do not address the cause. Without knowing what you are allergic to, you cannot avoid it and may need to take medication for life. Identifying the true cause is an important first step toward targeted treatment.
Q: Does the test hurt? Can children do it?
It hurts very little, feels like a light scratch, and there is no injection into the vein. Children from age 2 can have the test, with doctors closely monitoring throughout the process.
Q: What medications should be stopped before the test?
Antihistamines should be stopped at least 7 days before the test, all types, especially beta-blockers, which may increase risk during treatment if a severe allergic reaction occurs and may reduce the effectiveness of allergy medications.
Q: If the result shows an allergy, do I have to avoid that allergen for life?
The doctor will plan appropriate treatment, which may include avoidance, medication, or immunotherapy, which can reduce the body’s sensitivity to allergens over time.
Q: What is the difference between Skin Prick Test and Blood Test?
Skin Prick Test provides faster results (15–20 minutes), is highly accurate, and can test multiple allergens simultaneously. Blood tests require 3-5 ml of blood and results take about 1-2 weeks. Blood tests are usually done when Skin Prick Test is not possible, such as when antihistamines cannot be stopped, during pregnancy, or in uncontrolled asthma with breathing difficulty.
Q: Will getting tested really improve my life?
Once you know what you are allergic to, you can effectively avoid it and reduce medication use.
This helps improve quality of life, such as better sleep, improved work performance, especially if allergies have started to affect work or daily life.
Q: Is the Skin Prick Test expensive?
The cost of the test is reasonable compared to the accumulated expenses of buying allergy medications, repeated doctor visits, and the long-term impact on quality of life.
Skin Prick Test: The first step toward a better quality of life
Skin Prick Test is not just about identifying allergens but an investment in your health or the health of your loved ones.
When you know what you are allergic to, you can
- Avoid allergens precisely and effectively
- Reduce dependence on allergy medications in daily life
- Sleep better, wake up refreshed without nasal congestion or sneezing
- Work, study, and live fully without allergy symptoms interfering
- Receive truly appropriate treatment tailored to you
Don’t let allergies reduce your quality of life any longer. Consult a doctor to find the true cause and plan targeted treatment.
Dr. Krittecho Siripatsorn [W.20467]
Specialist in Internal Medicine, Allergy and Clinical Immunology
Internal Medicine Center
Phyathai 3 Hospital
