INTRODUCTION
Insect bites not only carry the potential to spread disease but also cause significant discomfort. DEET and other chemical pest-repellents are potentially neurotoxic.1 Natural repellents based on essential oils show very limited efficacy.2 Many patients do not tolerate mosquito netting.3
Ivermectin (IVM), a potent endectocide with a broad safety index used since the 1980s, acts through an unclear mechanism upon glutamate-gated chlorine channels.4 Studies support that the blood of vertebrates injected with ivermectin is lethal to mosquitos in a dose-dependent manner;5 however, oral (PO) and intravenous (IV) IVM are not approved for chronic use. On the other hand, the absorption rate of topical IVM is lower than other formulations, resulting in a safer, more appropriate drug for long-term use.6 Hence, topical IVM is approved for chronic use to treat demodex rosacea. Effects of topical IVM on mosquito bite prevention have not been previously published.
Ivermectin (IVM), a potent endectocide with a broad safety index used since the 1980s, acts through an unclear mechanism upon glutamate-gated chlorine channels.4 Studies support that the blood of vertebrates injected with ivermectin is lethal to mosquitos in a dose-dependent manner;5 however, oral (PO) and intravenous (IV) IVM are not approved for chronic use. On the other hand, the absorption rate of topical IVM is lower than other formulations, resulting in a safer, more appropriate drug for long-term use.6 Hence, topical IVM is approved for chronic use to treat demodex rosacea. Effects of topical IVM on mosquito bite prevention have not been previously published.
MATERIALS AND METHODS
Two patients were repeatedly bitten on the face at night by Ceratopogonidae, AKA "no-see-ums," small biting seasonal mosquitos (Figure 1). One caught and photographed a likely culprit (Figure 2). Neither patient tolerated mosquito netting at night, and both wished to avoid nightly application of potential neurotoxins such as DEET. Safer insect repellents containing essential oils did not work. They therefore applied 1% IVM cream to their faces before bed and assessed themselves for new bites each morning. They treated for 3 weeks on, then
off, and then on again.
off, and then on again.
RESULTS
Both noted complete prevention of mosquito bites on the nights
where 1% IVM cream was applied. Bites recurred after stopping
1% IVM cream. Complete prevention was again noted after
restarting 1% IVM cream.
DISCUSSION
Topical IVM prevented insect bites on the treated areas of the face. The pattern of recurrent bites after stopping IVM, and recurrent prevention after restarting IVM, provides further support for efficacy. Safety of topical 1% IVM cream is supported by its prolonged use as a treatment for lice and rosacea.7,8 While
