The subject invention is based upon the discovery that an antifungal agent can be delivered through the fingernail or the toenail of an infected human to treat onychomycosis by dissolving or dispersing the antifungal agent in a solvent system which is comprised of a combination of an alkyl lactate and Simmondsia chinesis seed oil. In accordance with this invention the antifungal agent is absorbed by and incorporated into the nail matrix by diffusing through the epithelium of the nail bed to reach the nail bed hyperkeratosis. The antifungal agent additionally penetrates into the ventral surface of the nail plate. The subject invention more specifically discloses an antifungal serum which is comprised of (1) an alkyl lactate, such as isoamyl lactate, (2) Simmondsia chinesis seed oil, and (3) an antifungal agent, such as tolnaftate or undecylenic acid.