** Thanks for contacting with your health concern. 1. Rash is a documented ADR [adverse drug reaction] of Omeprazole and some recent study do have suggested that Omeprazole may induce skin pigmentation [skin hyperpigmentation] PS. Omeprazole Induced Skin Hyperpigmentation Prasad Thota*, Nagakishore Ch, Kalaiselvan V, Gyanendra Nath Singh NCC-PvPI, Indian Pharmacopoeia Commission, Ghaziabad, UP, India 2. clinically significant skin hyperpigmentation may occur during the treatment with omeprazole and treating physicians should be aware of this phenomenon, and because the incidence of drug-induced hyperpigmentation is very variable thus you should talk with your attending physician as to how to proceed further. PS. under no circumstances you should stop-change- alter the dosage without first consulting with your doctor.