When acyclovir is used for a skin rash

Acyclovir is an antiviral medicine used for herpes simplex and varicella-zoster infections. Those infections may produce grouped blisters, painful sores or a painful band of blisters on one side of the body. The medicine limits viral replication; it is not an antibiotic, antifungal, steroid or general anti-itch treatment.

Eczema, contact reactions, heat rash, psoriasis, ringworm and scabies require different management. Appearance alone can be misleading, so using leftover acyclovir for an undiagnosed eruption can delay the treatment that matches its cause.

Take acyclovir only as prescribed for the diagnosed infection, follow the formulation-specific directions and complete the advised course. Tell the prescriber about kidney problems, pregnancy, breastfeeding and all other medicines. Maintain normal fluid intake unless another clinician has restricted it.

Avoid scratching or opening blisters, wash your hands after touching the area and do not share towels or personal items. Ask how to reduce transmission because precautions depend on the virus and the location of lesions.

Seek urgent medical assessment for a rash near the eye, eye pain or visual change; widespread blistering; sores involving the mouth or genitals; breathing difficulty; facial swelling; severe weakness or confusion; or a rapidly worsening eruption with fever. Prompt advice is also needed for newborns, people with weakened immunity and anyone who develops reduced urination or a new rash after starting the medicine.

Confirm which virus is suspected, whether testing is useful, which form of acyclovir is intended and what improvement to expect. Ask what to do after a missed dose, which side effects merit contact and how long the affected area may remain contagious.