Patch Testing (North American) Instructions

Patch Testing Instructions

North American Contact Dermatitis Group (NACDG) Series

Overview

Patch testing checks for delayed allergic contact dermatitis by placing small amounts of allergens on your back.

We often start with the NACDG screening series, a standardized North American panel that currently includes 89 common allergens. Based on your history, we may also test additional allergens or selected personal products.

Patch testing does not test for:

• Food allergies

• Medication allergies

• Seasonal allergies

Before Your Test

• Keep your back free of sunburn, tanning, and light treatments for 1 to 2 weeks before testing.

• Arrive with a clean, dry back.

• Do not apply lotion, cream, ointment, fragrance, or medicated topical products to the test area on the day of placement.

• Wear a loose shirt, bra, or top that you do not mind staining. The surgical marker can stain clothing.

• If your back is very hairy, clip or shave 1 to 2 days before testing if we ask you to.

• Tell us about all medications you are taking. Some medications, including steroids, biologics, and other immune-suppressing medicines, may affect results, and we may need to coordinate with your prescriber.

• Bring ingredient lists, containers, or photos of personal care products, workplace exposures, gloves, topical medicines, or other items you think may be triggering your rash.

• Keep the marker lines visible. Do not scrub or try to wash them off.

Test Week and Follow-Up

Patch testing usually requires 3 visits.

Visit 1

• Patches are applied to your upper back.

Visit 2 (About 48 Hours Later)

• Patches are removed.

• The skin is re-marked.

• We complete the first reading.

Visit 3 (About 2 to 5 Days After Removal)

• Final reading

• Review of results

• Some allergens react later, so this visit is very important.

Between Visits

• Keep the patches and ink markings dry.

• Avoid:

  • Showers on the back

  • Swimming

  • Hot tubs

  • Heavy exercise

  • Heat

  • Stretching

  • Friction

  • Scratching

• Do not apply soaps, lotions, creams, or ointments to the test area.

• If an edge lifts, reinforce only the outside tape.

• If a whole strip comes off:

  • Note the time

  • Take a photo

  • Call our office

• Keep the marker lines visible and do not scrub them off.

• Try to sleep in a way that limits rubbing on your back.

After Your Final Reading

• Mild redness and itching may last a few days.

• Stronger or blistering reactions can last up to several weeks.

• You can usually shower normally after the final visit, unless we tell you otherwise.

• Resume topical medicines on the tested area only after we tell you it is okay.

• Take a photo and contact us if a severe worsening or new reaction appears after you leave.

• Some reactions can appear or become stronger for several days after the final reading.

Do

• Keep all follow-up visits

• Wear loose, soft clothing

• Use a cool, dry compress for itching

• Continue antihistamines if previously approved

Don’t

• Get the test area wet

• Scratch or peel the tape

• Do heavy exercise, hot yoga, or use a sauna until the final reading

• Apply topical products to the test area

Call Our Office If

• You have severe burning, pain, or blistering

• You develop facial swelling, fever, or shortness of breath

• You have a major flare of your rash or rash elsewhere

• Patches come off early

• You think you may miss a reading