Differential Diagnosis of a Generalized Rash
Atopic dermatitis (Eczema)
Contact dermatitis
Drug reaction (Drug eruption)
Viral exanthem (nonspecific)
Urticaria (hives)
Poison ivy
Folliculitis
Insect Bites
Seborrheic dermatitis
Tinea corporis
Tinea versicolor (Pityriasis Versicolor)
Psoriasis (plaque psoriasis)
Psoriasis (Guttate psoriasis)
Psoriasis (pustular, erythroderma, and inverse psoriasis)
Candida
Keratosis pilaris
Pityriasis rosea
Lichen planus
Roseola (exanthem subitum or sixth disease)
Measles
Rubella
Scabies
Nummular eczema
Fifth disease (erythema infectiosum)
Lyme disease
Erythema multiforme
Heat Rash: There are 3 types. Miliaria rubra (prickly heat), Miliaria crystallina, Miliaria profunda.
Mycosis fungoides
Dermatitis herpetiformis
Id reaction (Autoeczematization reaction)
Scarlet Fever
Kawasaki’s disease
Unilateral lateral thoracic syndrome
Chickenpox (Varicella)
HIV acute exanthem
Lupus (subacute cutaneous)
Swimmer’s itch, Seabather’s eruption
Eruptive xanthomas
Erythema nodosum
Generalized granuloma annulare
Rocky Mountain Spotted Fever
Secondary syphilis
Disseminated varicella zoster
Toxic shock syndrome
Meningococcemia
Disseminated bullous impetigo
Stevens-Johnson syndrome
Sweet’s syndrome ((acute febrile neutrophilic dermatosis))
Transient acantholytic dermatosis (Grover’s disease)
Acute generalized exanthematous pustulosis
Dermatomyositis
Leprosy (Hansen’s disease)
Keratosis Follicularis (Darier Disease)
Further Reading
Am Fam Physician. 2010 Mar 15;81(6):726-734. https://www.aafp.org/afp/2010/0315/p726.html
Am Fam Physician. 2010 Mar 15;81(6):735-739. https://www.aafp.org/afp/2010/0315/p735.html