Acute systemic hypersensitivity reactions to semen are rare but may be life-threatening. Chronic or recurrent local reactions are more common and may be misdiagnosed as infective or nonspecific vaginitis. The antigen(s) involved in these reactions reside in a glycoprotein fraction of seminal plasma. Allergic vulvovaginitis may also occur in sensitized women when they are exposed to exogenous allergens such as drugs, food and infective agents during sexual activity. Skin testing and other relevant investigations are indicated when these disorders are suspected. Condom usage will prevent symptoms of coital allergy. Desensitization has had variable success in acute systemic hypersensitivity. Precoital antihistamines may modify local reactions.