Why are there ridges on my nails? (photo)

As Dr Paul has explained, the appearance of a brown line on your nail, known as melanonchia, is due to melanin within the nail. It's most often due to non-worrying causes. These include: Moles Freckles Fungal infection Pregnancy Trauma/injury (eg. from nail-biting) Bleeding under the nail Melanonchia due to moles commonly affect the thumbs, index fingers and big toes, like in your case. Of course, as you may have read, the internet will say that the big C word is a possible cause too (melanoma, a particularly aggressive type of skin cancer).

You’ve likely got chronic urticaria, and will need to take a doctor-prescribed course of anti-histamines to get rid of the itchy rash. No cause or trigger is found in 80% of people with chronic urticaria, in case you were wondering. It’s just one of those things that happen, unfortunately. Good news? It’s self-limiting, and responds very well to treatment (oral anti-histamines). The dents in your nails sounds like nails pitting (shown in picture below). There are several causes for nail pitting, of which psoriasis is an important cause to rule out.