Meyerson phenomenon, also known as halo dermatitis, halo eczema, or Meyerson nevus, refers to an eczematous reaction surrounding a pre-existing skin lesion. This phenomenon has been reported in melanocytic lesions and nonmelanocytic skin neoplasms. These include seborrheic keratosis, nevus sebaceus, benign nevus, molluscum contagiosum, dermatofibroma, stucco keratosis, lentigo, keloid, insect bite, dysplastic nevus, and malignant lesions such as melanoma, basal cell carcinoma, and squamous cell carcinoma. Meyerson phenomenon has also been reported around vascular lesions, such as vascular malformations, nevus flammeus, angiokeratomas, and lobular capillary hemangiomas.

Meyerson phenomenon is more common in young adults. There is no sex predilection. It typically occurs around a solitary lesion, and the trunk is the most common site. It is usually asymptomatic, but pruritus may be associated. Atopic history is a risk factor. Other triggers include sunburn, chemotherapy, Behçet disease, and treatment with interferon alpha. It may occur more frequently in the summer.

The pathophysiology of Meyerson phenomenon is thought to be immune mediated.