Cold sores, also known as herpes simplex labialis (HSL)
affect millions of Americans. While evidence of serologic
infection with herpes simplex virus type 1 (HSV-
1) approaches 80% in the general adult population, only about
30% of people have clinically apparent outbreaks. The painful
cluster of vesicles on an erythematous base is caused by the
herpes simplex virus. Herpes labialis is the most common
infection caused by HSV-1, whereas genital herpes is usually
caused by herpes simplex virus type 2 (HSV-2). However, oral/
genital sexual relations can allow the viruses to cross-infect;
consequently, HSV-2 is responsible for herpes simplex labialis
in 10-15% of cases. Intimate contact between a person who is
actively shedding the virus (or with body fluids containing the
virus) and an individual who is susceptible (who lacks antibodies
against the virus) is necessary for HSV infection to occur.1
The contact must involve abraded skin or mucous membranes.
HSV invades the epidermal and dermal cells and travels to
the sensory neurons (dorsal root ganglion) where latency is
established. The virus replicates in the neurons, leading to
recurrent outbreaks. The outbreaks are often induced by exposure
to ultraviolet light (sunlight and/or tanning beds), stress,
immunosuppression, the common cold, fatigue, fever (hence
the term “cold sore†or “fever blisterâ€), overexposure to the
wind, extremes in temperature, menstrual periods, pregnancy,
dental work, or lip trauma. Perioral laser resurfacing or
injection of perioral botulinum toxin or fillers can stimulate an
outbreak. Transmission of the virus can occur during primary
infection, during subsequent recurrent infections, and even
during periods of asymptomatic viral shedding.
At present, there is no cure for HSL, so theoretically, once contracted,
the infection remains for life. The initial HSV-1 infection
is often asymptomatic and may not be noticed, or a fever may
be the only symptom. When perioral lesions do occur with the
primary infection, the initial outbreak is often the most severe; recurrences are typically more attenuated as a result of antibody
production.2 Approximately one-third of patients who experience
the initial HSV-1 infection go on to have recurrent herpes
labialis (RHL). Most patients with RHL have less than two episodes
per year but 5-10% experience six or more recurrences per
year.3 The pain, embarrassment, and temporary disfigurement
of herpes lesions can be reduced by taking medication at the first
sign of prodromal symptoms, such as itching, tingling, and burning,
or by taking daily suppressive therapy. Most HSV infections
are self-limited. However, antiviral therapy shortens the course
of symptoms and may prevent transmission and dissemination.
Commercially available topical treatments are much less effective
than IV or oral systemic therapy. All treatments are
most effective if used at the first onset of symptoms.
I. Topical Antiviral Agents
1. Docosanol 10% Cream (Abreva®)
N-docosanol is a 22-carbon alcohol that has been FDA approved
as an OTC agent for treating RHL. Applying the cream five times
per day prevents fusion between plasma membranes and the
HSV-1 virus envelope, reducing the risk of intracellular entry with
subsequent viral replication. Ideally, docosanol is applied during
the prodromal stage, but it is still useful, even at a later stage at
shortening healing time and duration of symptoms.4
2. Acyclovir 5% Cream or Ointment (Zovirax®)
Acyclovir cream, FDA approved for RHL, has been shown to
reduce lesion healing time by 0.5-0.6 days and the duration of
pain by 0.3-0.4 days.5
3. Penciclovir 1% Cream (Denavir®)
Penciclovir cream, FDA approved for RHL, has been shown
to reduce healing time in two studies by 0.7 and by two days,
respectively, when compared with placebo controls.6,7 When
compared directly with topical acyclovir cream in a randomized
controlled trial with 124 subjects in each treatment group,
there was no statistical difference between the two agents
with respect to clinical healing time of herpetic lesions.2
4. Acyclovir 5% and Hydrocortisone 1% Cream (Xerese®)
This combination cream is FDA approved to treat RHL. In one
study of 120 subjects with lesions of HSL, 50 subjects received
the treatment combination cream and 70 subjects received the