Atopic Dermatitis (Eczema): Given the patient's history of seasonal allergies and the description of mildly itchy areas on both sides of the body, atopic dermatitis is a plausible diagnosis. It's a common condition that can be exacerbated by allergies and often presents with symmetric, itchy lesions.

Urticaria: This condition can cause itchy hives and can be triggered by allergies, infections, or other factors. The recent cold symptoms could be a contributing factor.
Contact Dermatitis: Although the patient denies contact with anything unusual, it's possible that an allergen or irritant was encountered without being recognized. This condition causes a skin reaction that can be itchy and appears on areas exposed to the offending substance.
Dry Skin (Xerosis): Especially during certain times of the year or with the use of harsh soaps, dry skin can become itchy. Given the patient's recent cold symptoms, which might include a dry environment due to increased heating, this is a consideration.

Cutaneous T-cell Lymphoma (Mycosis Fungoides): Although rare, this condition can present with itchy skin lesions and must be considered to avoid a delayed diagnosis. It's crucial to examine the skin lesions closely and consider a biopsy if they are atypical or persistent.
Bullous Pemphigoid: An autoimmune disease that can cause itchy blisters. It's more common in older adults and can be mistaken for other skin conditions, making it a "do not miss" diagnosis due to its potential for significant morbidity if not treated properly.

Pityriasis Rosea: A condition that causes a rash and can be itchy, often following a viral infection. It's less common but should be considered, especially if the rash has a characteristic "Christmas tree" distribution.
Dermatitis Herpetiformis: An autoimmune blistering disorder associated with celiac disease, characterized by intensely itchy blisters. It's rare but important to diagnose due to its association with celiac disease, which requires dietary management.