Atopic Dermatitis (Eczema): This is a common condition characterized by itchy, inflamed skin that can lead to a papular excoriated rash due to scratching. The fact that the rash is over the entire body and the patient is 22 years old, an age when atopic dermatitis can persist or recur, supports this diagnosis.

Contact Dermatitis: This condition occurs when the skin comes into contact with an allergen or irritant, leading to an itchy, papular rash. Given the widespread nature of the rash, an allergic reaction to something like a new laundry detergent or a component in personal care products is possible.
Psoriasis: Although psoriasis typically presents with well-defined, scaly plaques, in its early stages or in certain variants (like guttate psoriasis), it can appear as a widespread papular rash. The excoriated nature could be due to scratching.
Pityriasis Rosea: This condition starts with a single "herald patch" followed by a widespread, symmetrical rash that can be papular and itchy, potentially leading to excoriations.

Scabies: Caused by the mite Sarcoptes scabiei, scabies can present as a severe, itchy, papular rash that can be widespread. It's crucial to consider scabies due to its contagious nature and the potential for severe discomfort.
Syphilis (Secondary): In its secondary stage, syphilis can cause a wide range of skin manifestations, including a papular rash that can be found on the palms and soles, as well as the rest of the body. Given the potential seriousness of untreated syphilis, it's a diagnosis that must be considered.
Drug Reaction: Certain medications can cause widespread, itchy rashes as part of an allergic reaction. Identifying and stopping the offending drug is crucial, making this a "do not miss" diagnosis.

Papular Urticaria: This is a rare condition characterized by an itchy, papular rash due to an allergic reaction, often to insect bites or other environmental allergens.
Erythroderma (Exfoliative Dermatitis): A condition where almost the entire skin surface is involved, leading to redness, scaling, and sometimes a papular rash. It can be primary (idiopathic) or secondary to other skin conditions or systemic diseases.
Keratosis Pilaris: While typically presenting as small, rough patches on the skin, in some cases, it can cause a more widespread, itchy, papular rash, especially if scratched or irritated.