Acyclovir is available in various dosage forms such as creams, eye preparations, tablets, and capsules. Side effects after using tablets or capsules include dizziness and headache, joint pain, nausea and vomiting, diarrhea, loss of appetite, thirst, itchy skin, insomnia, and menstrual disorders. Side effects of cream preparations are mild pain, burning, stinging and itching. Eye preparations side effects include mild pain and burning sensation. Acyclovir is mainly used for the treatment of herpes simplex or herpes zoster infections, including herpes simplex infection of the lips or genitals, herpes simplex infectious keratitis, herpetic eczema, herpetic erythema multiforme, herpes simplex encephalitis, and many other conditions. It is contraindicated in patients who are allergic to any of the ingredients of acyclovir, and should be used with caution in pregnant and lactating women, and in those with abnormal liver or kidney function. If you need to use this drug, please consult a professional doctor, follow the doctor’s instructions, and use the drug reasonably.