Allergy skin tests are the best and most reliable method of diagnosing allergies. Medications may influence the interpretation of skin testing. Antihistamines interfere with prick and intradermal skin tests, while they do not suppress patch tests. Some other medications also have influence on allergy skin tests. Its important to know the suppression mechanism and the duration of the inhibitory effect of these drugs on the skin test to get correct interpretation, which would be a valuable guide in allergen identification and avoidance in treatment of allergies. Allergic diseases are common and bothering medical problems in pregnant patients. Its generally recommended to avoid all medications during pregnancy, if possible. But sometimes antihistamines are needed to be used in the treatment of allergic diseases regarding the benefit/risk ratio. In such cases, antihistamines should be carefully chosen. Considering the animal and human data available, chlorpheniramine seems to be the antihistamine to choose with the least risk.