There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Pruritus without Erythema as an Allergic Reaction
- Pruritus, or itchiness, can occur without erythema, or redness, and may be associated with various conditions, including allergic reactions 1, 2, 3.
- Allergic contact dermatitis (ACD) is a common inflammatory skin disease that can cause pruritus, but it is typically characterized by eczematous dermatitis with erythema, edema, vesicles, scaling, and intense itch 4.
- However, pruritus without erythema can also be a symptom of other conditions, such as cutaneous pruritus, which is a disease characterized by itch without an observable rash 1, 3.
- Cutaneous pruritus can be classified into two categories: localized and generalized, and may be caused by various factors, including systemic diseases, drug-induced itch, psychogenic itch, or chronic pruritus of unknown origin (CPUO) 1, 3.
- The diagnosis and treatment of pruritus without erythema can be challenging, and may require a comprehensive evaluation, including a thorough skin examination, laboratory tests, and patch testing with suspected allergens 4, 5.
- Treatment approaches for pruritus without erythema may include trigger avoidance, liberal emollient use, limiting water exposure, and administration of oral antihistamines and topical corticosteroids 5, 3.