short presentation on basics of patch test made as a part of residency program in dermatology

1. DR.SABHA TALIB
NEAZEE

2. To elicit an immune response by
challenging already sensiitized
person to defined amount of
allergen and assessing the degree of
response.

4.  Stop all anti immunosuppressants if feasible.
 Systemic agents before 3 months.
 Biologics before 6 months.
 Topical corticosteroids before 2 weeks.
 Prednisolone < 15mg according to ROOK’S
TEXTBOOK OF DERMATOLOGY and
prednisolone < 10mg according to BRITISH
ASSOCIATION OF DERMATOLOGISTS can be
continued.
 Discontinuation of antihistamines is desirable
before 48 hours.

5.  Prohibition of wetting the back.
 Prohibition of performing activities that
increase sweating.
 Probable local symptoms such as itching .
 Prohibition of exposing themselves to UVR
upto fifteen days prior to testing.

6.  Prohibition of wetting the back.
 Prohibition of performing activities that
increase sweating.
 Probable local symptoms such as itching .
 Prohibition of exposing themselves to UVR
upto fifteen days prior to testing.

7.  Test site-Back
Lateral aspect of upper arm
 Exposure time- 48 hour application time with
readings taken 1 hour after removal and then
48 hours later. Day 2 and day 4.
 If only 1 patch test reading- day 4.
 3rd reading- 5 to 7 days if possible.

14.  Positive reaction to more than five non
related substances.
 Poly sensitization.
 Repeat testing of selected allergens two
months later.

16.  Compound allergy-Positive allergic patch test
is seen to a finished product but tests with
ingredients are negative.
 Quenching – inhibition of response.

17.  European environmental and contact
dermtitis research group,EECDRG- 28
allergens.
 British society for cutaneous allergy, BSCA-
39 allergens
 North american contact dermatitis group,
NACDG- 65 allergens.
 Indian standard series- 20 allergens.

18.  The allergens are tested in duplicate on back
and irradiated with UV light( most often UV-A
5j/cm2
 1st reading- immediately post irradiation.
 2nd reading- 2 days post irradiation.

19.  Open- allergen is applied uncovered on the
upperarm or upperback twicedaily for 2 days
 Semiopen- direct application of liquid with a
cotton tip applicator. 1 cm2. after complete
evaporation, test site is covered with acrylic
tape.
 Reading day 2 AND DAY 4.

20.  0.1ml of test material is applied twice daily
to flexor aspect of forearm. 25 cm2.
 1st reading – after 1 week.
 May be performed for upto 21 days.