Herpes may refer to either the "disease" or to "reptiles". The diseases are usually either "herpes simplex" or "herpes zoster".

1. An acute infectious, usually self-limited, disease believed to represent activation of latent varicella-zoster virus in those who have been rendered partially immune after a previous attack of chickenpox: Further terms with the same meaning as herpes zoster are "shingles", "zoster", "zone", and "acute posterior ganglionitis".
2. A reactivation of the same Herpes virus that is responsible for chicken pox: Herpes zoster results in a painful blistery red rash that is confined to one side of the body.
3. Eruptions along a nerve path often accompanied by severe neuralgia or an acute viral disease caused by a herpesvirus: The herpes zoster is the same virus that causes chickenpox.

Characteristics include inflammation of spinal ganglia with pain and a vesicular eruption along the area of distribution of a sensory nerve.

It sometimes accompanies diseases such as pneumonia, tuberculosis, and lymphoma; and it may be triggered by trauma or injection of certain drugs.

In some cases, it appears without any apparent reason for activation.

It involves the sensory ganglia and their areas of innervation, characterized by severe neuralgic pain along the distribution of the affected nerve and crops of clustered vesicles over the area of the corresponding dermatome, and it is usually unilateral and confined to a single or adjacent dermatomes.

Shingles involving the ophthalmic nerve of the eye with a vesicular (small skin blister) erythematous (redness of the skin) rash along the nerve path (forehead, eyelid, and cornea) preceded by lancinating (sharply cutting) pain: Symptoms of herpes zoster ophthalmicus include swelling of the eyelid, a rash of the forehead, eye redness and sensitivity to light, and fever.