Differential Diagnosis for Facial Papules after Starting Landscape Work

• Single most likely diagnosis
  • Contact dermatitis: This is the most likely diagnosis due to the exposure to new plants and substances while doing landscape work, which can cause an allergic reaction or irritant contact dermatitis, leading to facial papules.
• Other Likely diagnoses
  • Photoallergic contact dermatitis: Similar to contact dermatitis but involves a reaction to substances that become allergenic when exposed to sunlight, which is common in outdoor work like landscaping.
  • Irritant contact dermatitis: A non-allergic reaction to substances that irritate the skin, such as certain chemicals or plants encountered during landscape work.
  • Insect bites: Mosquitoes, ticks, and other insects encountered during outdoor work can cause papular lesions.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Lyme disease: Although less common, tick bites during landscape work can transmit Lyme disease, which initially presents with a characteristic "bull's-eye" rash (erythema migrans) but can be mistaken for a papule.
  • Leishmaniasis: In endemic areas, sand fly bites can transmit leishmaniasis, which can cause skin lesions that might initially appear as papules.
• Rare diagnoses
  • Phytophotodermatitis: A rare condition caused by contact with certain plant substances (like furanocoumarins in parsnip or lime) followed by exposure to sunlight, leading to blistering and potentially papular lesions.
  • Berloque dermatitis: A condition caused by the use of certain perfumes or fragrances that contain bergamot oil, which can react with sunlight to cause pigmented contact dermatitis, potentially presenting with papules.