Differential Diagnosis for Itchy Rash
- Single most likely diagnosis
- Scabies: The patient's symptoms of an itchy rash, worsening itching, and a sensation of "critters" crawling on him, especially after staying in a hotel, are highly suggestive of scabies. Scabies is a contagious skin infestation caused by the mite Sarcoptes scabiei, often acquired through direct skin-to-skin contact or by sharing personal items, which could have been contaminated in the hotel.
- Other Likely diagnoses
- Bed bugs: Given the patient's recent travel and hotel stay, bed bug bites are a plausible cause for the itchy rash. Bed bugs can cause significant discomfort and their bites often result in itchy, red welts.
- Contact dermatitis: This could be a reaction to new soaps, laundry detergents, or other products used during travel, leading to an itchy rash.
- Flea bites: If the hotel room had fleas, either from previous pets or infestation, this could cause an itchy rash.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Neurological disorders (e.g., neuropathy, delusional parasitosis): Although less likely, conditions that affect the nervous system can cause sensations of itching or crawling without an actual skin infestation. Delusional parasitosis is a psychiatric condition where the patient has a fixed, false belief of being infested with parasites, which is crucial to differentiate from actual infestations.
- Rare diagnoses
- Ectoparasitic infestations other than scabies or bed bugs (e.g., lice, ticks): While less common, other ectoparasites could potentially cause similar symptoms.
- Allergic reactions to medications: If the patient started any new medications during travel, an allergic reaction could manifest as an itchy rash.
- Systemic conditions with skin manifestations (e.g., renal or liver disease): Certain systemic diseases can cause pruritus (itching) without a clear rash, though this would be less likely given the acute onset and description of a rash.