Hello. Thank you for writing to us at healthcaremagic I will keep a possibility of genital herpes, as the reason for blisters and the resulting hyperpigmentation/dark shades. Genital herpes, classically presents as grouped, discrete, vesicles which soon rupture to form erosions. The erosions may be painful Or have a burning sensation over them. The hyperpigmentation/black shading is most likely due to post-inflammatory hyperpigmentation (PIH), which is a non-specific reaction to any inflammatory insult to the skin. Genital herpes is usually transmitted by direct/intimate contact with an infected sexual partner. The infection can also be transmitted even when the infection is clinically silent as low grade multiplication of the virus goes on inside the body and therefore the virus is shed from time to time from infected genital surfaces, although in small numbers as compared to when there are active herpetic sores. The sores of herpes are fairly characteristic to be diagnosed visually. However, in the absence of sores a blood test for herpes e.g Hsv ELISA for type I and type 2 virus, would be helpful in either confirming or ruling out genital herpes. Regards