Differential Diagnosis for Generalized Itching and Eosinophilia

Single Most Likely Diagnosis

• Atopic Dermatitis (Eczema): This condition is characterized by generalized itching, and while eosinophilia can be present, a 7% eosinophil count is not unusually high in this context. The presence of itching and the potential for skin lesions make atopic dermatitis a strong consideration.

Other Likely Diagnoses

• Allergic Contact Dermatitis: This is a skin reaction that occurs after contact with an allergen, leading to itching and potentially eosinophilia. Given the generalized nature of the itching, it might be more challenging to identify a specific allergen, but it remains a plausible diagnosis.
• Urticaria: Although typically associated with hives, chronic urticaria can present with generalized itching and may have an accompanying eosinophilia. The absence of hives does not rule out this diagnosis entirely.
• Drug Reaction: Certain medications can cause generalized itching and eosinophilia as part of a drug reaction. This would be especially considered if the patient has recently started new medications.

Do Not Miss Diagnoses

• Hypereosinophilic Syndrome (HES): While less common, HES is a condition characterized by persistent and marked eosinophilia that can lead to organ damage. Generalized itching can be a symptom, and it's crucial to rule out this condition due to its potential severity.
• Malignancy (e.g., Lymphoma, Leukemia): Certain cancers can present with generalized itching and eosinophilia. Although less likely, missing a diagnosis of malignancy could have severe consequences, making it essential to consider and rule out.
• Parasitic Infections: Infections like hookworm or strongyloidiasis can cause eosinophilia and generalized itching. These are important to consider, especially if the patient has a history of travel to endemic areas.

Rare Diagnoses

• Eosinophilic Pustular Folliculitis: A rare condition characterized by eosinophilia and skin lesions, which could potentially present with generalized itching.
• Churg-Strauss Syndrome (Eosinophilic Granulomatosis with Polyangiitis): A rare autoimmune condition that can cause eosinophilia, skin lesions, and potentially generalized itching, among other systemic symptoms.

Given the information, starting with levocetirizine (an antihistamine) and topical steroids could be a reasonable initial approach to manage symptoms, especially if an allergic or atopic component is suspected. However, if the symptoms are severe, do not respond to initial treatment, or if there are concerns for a more serious underlying condition, oral steroids or further diagnostic workup may be necessary. The differential diagnosis provided here should guide further investigation and management.