Dyshidrotic Eczema (Pompholyx): This condition is characterized by the appearance of small, itchy blisters on the hands and feet, particularly on the sides of fingers. It's a common condition that matches the symptoms described.

Contact Dermatitis: This is a type of skin inflammation caused by contact with irritants or allergens, which can lead to itchy blisters. Given the location on the sides of fingers, exposure to something in the environment could be a plausible cause.
Atopic Dermatitis (Eczema): While more commonly associated with dry, itchy skin, atopic dermatitis can sometimes present with small blisters, especially if the skin is scratched excessively.
Irritant Contact Dermatitis: Similar to contact dermatitis but caused by substances that directly irritate the skin, such as detergents or certain chemicals.

Herpes Simplex Infection: Although less common on the sides of fingers, herpes simplex can cause fluid-filled blisters. It's crucial to distinguish this from other causes due to its infectious nature and potential for complications.
Scabies: Caused by a mite, scabies can lead to severe itching and small blisters, especially in areas like the fingers. Missing this diagnosis could lead to prolonged suffering and transmission to others.
Bullous Pemphigoid: An autoimmune disease that can cause large, itchy blisters. While less common, it's a serious condition that requires prompt treatment.

Bullous Dermatoses: A group of rare skin conditions characterized by the formation of blisters. These include conditions like pemphigus and epidermolysis bullosa acquisita.
Aquagenic Palmoplantar Keratoderma: A rare condition that causes blisters on the palms and soles after exposure to water, which could potentially affect the sides of fingers in some cases.
Keratosis Pilaris: While typically presenting as small, rough patches on the skin, some forms can lead to blister-like lesions, although this is less common and usually not itchy.