Hi,
This may be a case of irritant dermatitis, dishydrotic eczema, contact dermatitis or a fungal infection. Do you bite your nails? Do you use to have the habit of thumb sucking?
Irritant dermatitis may be due to frequent and repeated exposure to certain irritants like soaps, detergents and other chemicals like chalk for instance. Contact dermatitis may be due to a particular material or object in which the skin reacts to. The skin may show a red rash which may be itchy and later excoriate. Dishydrotic eczema may start as blister with a clear fluid. They may later cause itchiness. Scratching the area may cause further irritation and involvement of normal skin. An associated fungal infection may present with scaling and aggravate the itchiness. The skin condition may last for a long time.
Are your nails involved?
The thing with a dermatitis is that, there is no definite treatment. Moisturizers and corticosteroids are the mainstay for therapy. Microscopic evaluation of the skin scrapings will be able to help define an underlying fungal infection.
It all started out as a small crack in my skin, and it eventually kept getting bigger until it covered about half my thumb. It doesn't seem to be getting bigger anymore.
Hi.
If there is any history of prior prolonged water exposure like washing the dishes etc, any exposure to detergents and other chemicals, then this could be causing the condition.
Cracking of the skin may due to dryness or thinning of the skin secondary to irritation. A cracked skin encourages infection to set in or it could be a manifestation of an infection or dermatitis itself.
At this point, I still think of a dermatitis as a differential. A consult with a dermatologist will help prescribe the right medications. Corticosteroids usually alleviate the problem but in the presence of cracked skin and abrasions, topical medications may only aggravate the condition.
Discuss this with your physician.