Riehl melanosishttps://en.wikipedia.org/wiki/Riehl_melanosis
Riehl melanosis is a form of contact dermatitis, beginning with pruritus, erythema, and pigmentation that gradually spreads which, after reaching a certain extent, becomes stationary. Sun exposure after the use of some perfumes or creams may the cause of the disease.

      References Riehl Melanosis 32491369 
      Riehl melanosis (RM), commonly called pigmented contact dermatitis, is considered an acquired form of allergic contact dermatitis, typically to fragrance and other ingredients of cosmetic products. Although it is considered as a dermatitis, it presents clinically with hyperpigmentation over the face and shows pigment incontinence with minimal eczematous changes on histology. The condition is more commonly seen in dark-skinned people, causing an important psychosocial impact. A recent study showing the higher effectiveness of mid-fluence QSNY 1064-nm laser in targetting the deep pigmentation of RM has also been conducted. Another study used a combination of therapies to include low-fluence, 1064-nm, Q-switched Nd: YAG laser, hydroquinone cream, and oral tranexamic acid, with the majority of patients experiencing significant improvement.
       Research Advances in the Treatment of Riehl’s Melanosis 37168093 
      Riehl's melanosis (RM) is a contact photodermatitis, with fast progressive gray-brown skin pigmentation as the main manifestation, which can seriously affect the psychology and physiology of patients. Currently, although the etiological factors of Riehl's melanosis is still be unknown, the existing literature proves clearly the cause of it is related to the contacting with suspected allergens. For decades, there has been no standard method for the treatment of RM, but with both conventional drug therapy and laser therapy having been attempted. Topical application of bleaching agents is mainly used as an auxiliary treatment modality. The laser treatment modality remains a hot spot, among which Q-switched Nd:YAG laser is well received for RM. Positive outcomes have been achieved by the combined treatment modalities attempted in recent years also achieve positive outcomes.