Primary oral infection with the herpes simplex virus (HSV) typically occurs at a young age, is asymptomatic, and is not associated with significant morbidity. After primary oral infection, HSV may persist in a latent state in the trigeminal ganglion and later reactivate as the more common herpes labialis, or "cold sores." Common triggers for reactivation are well known and include ultraviolet light, trauma, fatigue, stress, fever, inflammation, and menstruation. These lesions affect up to 45 percent of the U.S. population. They classically manifest as a well-localized cluster of small vesicles along the vermilion border of the lip or adjacent skin. The vesicles subsequently rupture, ulcerate, and crust within 24 to 48 hours. Spontaneous healing occurs over seven to 10 days. In immunocompetent patients, herpes labialis usually is mild and self-limited. However, pain, swelling, and cosmetic concerns may prompt physician consultation. Orally administered antiviral agents, such as acyclovir (Zovirax) or valacyclovir (Valtrex), have a modest clinical benefit if initiated during the prodrome. Topical treatment with 1% penciclovir cream (Denavir) may reduce healing time and pain slightly, even if initiated after the prodrome. However, reduction in healing time with systemic or topical agents is modest. Squaric acid dibutyl ester (SADBE) is a topical immunotherapeutic agent used in the treatment of verruca vulgaris and alopecia areata. During a recent FDA Compounding Advisory Committee Meeting, it was recommended that squaric acid dibutylester be included on the list of bulk drug substances allowed for use in compounding under section 503A of the Federal Food, Drug, and Cosmetic Act. And SADBE has now been so listed under section 503A. A study completed by Lee et al of 29 patients with recalcitrant warts demonstrated complete clearance in 69% of patients with application every 2-4 weeks. Silverberg et al showed a complete clearance in 58% of patients (n=61) when SADBE was applied 3 times weekly. SADBE has also been used with some success in the treatment of alopecia areata. In a review of the literature, Rokhsar et al noted a 50% to 60% success rate of SADBE in use for hair re-growth in this population. SADBE has been reported to cause eczema, lymphadenopathy, blistering, allergic contact dermatitis, skin hypopigmentation, a burning sensation after application, and systemic reactions including fever and arthralgias. A study completed by Oglio et al of eight patients treated with SADBE for warts noted only mild and well tolerated side effects of erythema, desquamation, cutaneous edema, pruritus, burning, and pain. SADBE induces a delayed-type hypersensitivity response which in warts, is believed to induce the killing of virally infected cells by cytotoxic lymphocytes. This influx of lymphocytes into lesional Page 4 of 14 tissue may also enhance the recognition and processing of viral antigens, leading to clonal expansion of effector cells. It is hoped that SADBE will offer subjects a safe and effective therapeutic option to decrease the frequency and severity of future herpes labialis outbreaks through these mechanisms. A placebo-controlled clinical study completed at Massachusetts General Hospital showed that squaric acid prevented recurrence of herpetic lesions. The effect of SADBE of delaying new herpes labialis outbreaks was highly significant (p\<0.01) as compared to placebo.