Please suggest topical steroid creams for my cracked itchy skin on my right hand thumb finger. why did it happen specifically only to one finger?

Hand Eczema: Hand eczema (also known as hand dermatitis) is a common condition affecting up to 10% of the population. It results from a combination of factors, both internal (e.g. Your genetic make-up), and external (e.g. Contact with irritants and allergens such as chemicals). Treatment is avoidance of allergens and topical steroids like vanos and emollients like cerave cream.

Hand eczema: Hand eczema is like that. If you can't explain why it happens to your thumb ( as the result of some exposure maybe?) we won't be able to explain it either. Hand eczema often requires more potent steroids than other parts of your body. Fluocinonide 0.05 % ointment or triamcinolone 0.5% ointment are reasonable choices. Use should be minimized to the level that keeps the rash under control.