Australian Birth Defects Society

A Society devoted to the study of birth defects


MotherSafe is a free telephone service for the women of NSW, based at the Royal Hospital for Women, Randwick.

August means: Cold sores

Iím seven weeks pregnant and havenít had a cold sore since I was seventeen years old. A couple of days ago one started to form and I went to the pharmacy to get some cold sore cream. The pharmacist said I mustnít use the acyclovir cream as it is a pregnancy category B3 and caused birth defects in animals. The cold sore is getting bigger and more painful, is there anything I can do?


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The usual treatment for cold sores is to use an antiviral cream containing aciclovir. A more recently available treatment is a single dose of oral famciclovir, available over the counter from the pharmacist.

While having a cold sore in early pregnancy is not expected to increase risk for your baby, they are painful and contagious, as well as cosmetically undesirable. The aciclovir in over the counter creams is not expected to increase pregnancy risk, as it is a small dose on the skin, and has been used in many pregnant women in oral (systemic) doses to treat genital herpes and other viral infections in pregnancy. The category B3, relating to animal studies, is irrelevant in the context of the available human pregnancy data. If cold sores are severe, your GP may prescribe the oral form of aciclovir or valaciclovir. The recently available over the counter antiviral tablets famciclovir is also not expected to be problematic, but as human pregnancy data has not been collected to date, the older medications (requiring a script from your GP) are preferred.

Lysine is an amino acid which is used by some people as a complementary treatment for cold sores. At present there is not a lot of scientific data to support the use of lysine for this purpose, but lysine is also not expected to increase pregnancy risk when used in recommended dosages.

Topical, non-medicated patches are used to improve the cosmetic appearance and are safe to use in pregnancy.


A factsheet is available to read or print out here:




Page updated 30 August 2016

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