**5.3.1** *β***-blockers**

Contact allergy to topical *β*-blockers is a well-recognized side-effect of glaucoma treatment [**38-41**]. Sensitization may be singly to agents such as timolol, befunolol, levobunolol, or, more rarely, to multiple *β*-blockers in a single patient.

A closed patch test, usually used in clinical practice for the diagnosis of allergic contact dermatitis, is often sufficient to show *β*-blockers contact allergy. However, there may be difficulties in obtaining positive patch tests to *β*-blockers, as showed in earlier reports [**42- 43**]. Poor penetration through intact skin on the back, where patch testing is normally applied, may be a factor.

#### **5.3.2 Antiviral drugs**

Topical antiviral drugs are frequently used, but although repeated applications can lead to contact reactions **[44-45]**, adverse cutaneous reactions are not commonly observed. Allergic contact dermatitis caused by acyclovir is rare, with only 20 studies reported **[46-48].** Because of the doubtful reactions with antiviral, especially acyclovir, and in view of the suggestive clinical history, we recommend the scratch–patch test followed by repeated open application test (ROAT).
