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Allergic Drug Reaction (ADR) and Allergy Testing by
Dr. Wong Soon Tee

Allergic drug reaction is an unintended side effect of a drug and it ranges from minor rash to life threatening reaction.

Why Choose Dr. Wong Soon Tee

Friendly & Experienced Specialist

Dr. Wong connects well with his patients & he is a specialist with over 30 years of experience.

Dedicated & Focused Patient Care

Dr. Wong will manage every step of his patient’s skin healing journey.

Safe & Effective Treatments

We offer a selection of carefully curated FDA & HSA-approved treatments that give effective results.

Dr. Wong Soon Tee

Consultant Dermatologist
Care and Professionalism Refined by Over 30 years of Dermatology Experience
  • MBBS, Yong Loo Lin School of Medicine, Singapore
  • MRCP. Member of Royal College of Physicians, United Kingdom
  • FAMS, Fellow of Academy of Medicine, Singapore
  • Adjunct Assistant Professor, National University of Singapore
  • Visiting Consultant, University Dermatology Division, National University Hospital
  • Visiting Consultant, Aesthetic Plastic Surgery Centre, National University Hospital

Allergic Drug Reaction (ADR) and Allergy Testing

Allergic drug reaction is an unintended side effect of a drug and it ranges from minor rash to life threatening reaction.

However, an allergy reaction to a drug is often misdiagnosed, over-diagnosed, or not reliably documented e.g. penicillin allergy. This becomes a problem when penicillin or related drugs e.g. Amoxycillin is essential and required by doctors to treat certain diseases and there is no better alternative. In such scenarios, a controlled allergy testing is required to see if the documented allergy is really true or not. If the testing shows that there is no allergy, then the drug can be safely used again.


Skin Reaction & Time Interval

There are 2 broad groups of drug allergy reaction and it is co-related to the time lapse of drug intake:

  • Immediate reaction: rash erupt immediately or within 1–6 hours following drug intake
  • Delayed reaction: several hours to days or weeks later

Skin Reaction

Time Interval

Hives; shock with low blood pressure

Typically within 1h, in rare cases up to 6h after exposure (immediate)


2-14 days after start of drug use (delay)

Extensive Pustules (AGEP)

1-12 days after start of drug use (delay)

Extensive Blisters (SJS/TEN)

4-28 days after start of drug use (delay)

Rash with systemic symptom (DRESS)

2-8 weeks after start of drug use (delay)

Various ways to do Drug Allergy tests

  • Skin Test

    Skin testing plays an important role in the diagnosis of allergy. Prick and intradermal test reactions are read and interpreted after 15 min. In the case of rash eruptions, late readings after 24, 48 or 72 hour may be necessary (e.g., when investigating amoxicillin eruptions). Sometimes, skin test reactions can even occur after more than 1 week.

  • Blood Tests

    Blood tests to measure specific IgE antibodies to a limited range of drugs (e.g. penicillin, amoxicillin) are available. However, it is not possible to conclusively detect or exclude drug allergy solely on the basis of blood tests.


    Blood test results can only be interpreted together with patient history/clinical findings and possibly skin testing.

  • Provocation Tests

    Provocation tests are necessary when the drug allergy cannot be identified with sufficient reliability on the basis of history, skin testing, and blood test investigations; and when the benefit of result obtained from provocation testing outweighs the risks. In cases of suspected and low likelihood of reactions to drugs that are essential (e. g., pain killers, antibiotics, local anesthetics), provocation tests are necessary and useful. In-patient medical supervision is required when provocation tests have the potential to trigger systemic reactions.

Restore Your Skin

Call Assurance Skin Clinic at +65 6694 1121 for an appointment with Dr. Wong to evaluate your drug allergy and the need for allergy testing now.

Book an Appointment

Allergy Test Will Not Be Done In The Following Situations:

  • Pregnancy and breastfeeding

  • Potential allergic reactions that may be beyond medical control (e.g. uncontrolled asthma, serious life threatening allergy)

  • Severe pre-existing diseases that carry an increased risk despite essentially controllable reactions (e. g., severe heart disease, severe asthma).

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