This study evaluates the safety and efficacy of SADBE in the prevention of recurrent herpes labialis in adults. Two-thirds of the participants will receive a SADBE solution, while the other third will receive only the vehicle as a placebo control. The solutions will be administered topically to the patient's arms. The study will compare a single-arm application versus a two-arm application versus two placebo doses on the arm.

Inclusion Criteria:

• Age ≥18
• Clinical diagnosis of herpes labialis, which may be made at the screening visit based on the patient's self-reported history of symptoms. An active herpes labialis outbreak at the time of entry into the clinical trial will neither be required nor will be an exclusion criteria.
• Self report having four or more episodes of herpes labialis in the past 12 months

Exclusion Criteria:

• People that have had treatment with anti viral therapy within 2 weeks before sensitization dose.
• Pregnant or lactating females.
• Current or recurrent non-herpetic infection or any underlying condition that may predispose to infection or anyone who has been admitted to the hospital due to bacteremia, pneumonia or any other serious infection.
• Therapy with glucocorticoid or immunosuppressants at time of recruitment or within past 4 weeks, except for inhaled corticosteroids for asthma or topical steroids in sites other than face.
• History of malignancy (except patients with surgically cured basal cell or squamous cell skin cancers)
• History of organ transplantation
• HIV-positive status determined by history at screening or known history of any other immunosuppressive disease.
• Severe co-morbidities (diabetes mellitus requiring insulin, CHF (EF<50% at baseline will be exclusionary) MI, CVA or TIA within 3 months of screening visit, unstable angina pectoris, oxygen-dependent severe pulmonary disease
• History of exposure to squaric acid or squaric acid dibutyl ester.
• Known hypersensitivity to DMSO
• Any condition judged by the investigator to cause this clinical trial to be detrimental to the patient.
• Subject is currently enrolled in another investigational device or drug trial(s), or subject has received other investigational agent(s) within 28 days of baseline visit.
• Previous or current participation in a clinical trial of SADBE to treat herpes labialis.