3. Topical Immunotherapy: Step by Step

Colombina Vincenzi¹, Benedetta Marisaldi¹ and Antonella Tosti²

(1)

Dermatology, Private Hospital Nigrisoli, Bologna, Italy

(2)

Fredric Brandt Endowed Professor of Dermatology, Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, USA

Colombina Vincenzi

Keywords

Alopecia areataAlopecia areata of the eyebrowsAlopecia areata of the beardSquaric acid dibutylesterDiphenylcyclopropenoneTopical immunotherapySensitizationHair regrowthT-lymphocyteProinflammatory cytokines

Introduction

Topical immunotherapy is a very effective treatment for AA. It is not recommended when the disease is acute and involves less than 10% of the scalp, in these cases, topical and/or intralesional steroids may a better option (See Chap. 9).

Topical immunotherapy consists of induction and periodic elicitation of an allergic contact dermatitis by topical application of potent contact allergens that are not present in the environment. Chemicals commonly used include squaric acid dibutylester (SADBE) and diphenylcyclopropenone (DPCP) diluted in acetone.

Characteristics of the Chemicals (Table 3.1)

Squaric acid dibutylester (SADBE) is synthesized by esterifying squaric acid. It is not present in the environment, and there are no possibilities of cross-reaction with other chemicals, nor is it mutagenic. Contact with water should be avoided, because of the instability of the substance. It must be kept in the dark and at 4–6 °C.

Table 3.1

Characteristics of SADBE and DPCP

SADBE (Squaric acid dibutylester)	DPCP (Diphenylcyclopropenone)
Not present in the environment	Not present in the environment
No cross reaction with other chemicals	Strong sensitizer
Not mutagenic	Less expensive than SADBE
Should be kept at 4–6 °C	Can be kept at room temperature
Should be kept in the dark	Destabilized by light

Diphenylcyclopropenone (DPCP) , on the other hand, needs to be purified because it may contain mutagenic contaminants. It is less expensive than SADBE and can be kept at room temperature.

How to Induce Sensitization

Before starting treatment, it is necessary to sensitize patients. Apply a closed patch test with a 2% solution of SADBE or DPCP (Fig. 3.1a) diluted in acetone on the scalp for 48 hours (Fig. 3.1b, c).

../images/440271_1_En_3_Chapter/440271_1_En_3_Fig1_HTML.png — Fig. 3.1

(**a–c**) Put three drops of SADBE 2% or DPCP 2% on a tape for patch test and then apply on the alopecic area of the scalp. Cover immediately with a bandage in order to fix the patch test

The patient must be instructed not to wash their head and to take care not to remove the patch before 48 hours. Avoiding scalp light exposure is also recommended, as for the whole treatment period.

The patch test should not be applied on the arms due to the risk of post inflammatory pigmentary abnormalities or flare up during the treatment.

Note: Do not sensitize on the arm! Risk of pigmentary abnormalities and flare up during treatment!

After 10–15 days, an allergic reaction will appear on the site of the patch test (Fig. 3.2).