Wood lamp is used to diagnose?
**Core Concept**
A Wood's lamp is a diagnostic tool used in dermatology to detect fungal and bacterial infections, as well as other skin conditions. It emits ultraviolet (UV) light, which causes certain microorganisms to fluoresce, making them visible to the naked eye.
**Why the Correct Answer is Right**
The Wood's lamp works by exciting the porphyrins produced by certain microorganisms, such as Pityrosporum ovale, causing them to fluoresce at 360-400 nanometers. This is a result of the energy from the UV light being absorbed by the porphyrins, which then emit light at a longer wavelength. The fluorescent light can be observed as a blue or yellowish hue on the skin.
**Why Each Wrong Option is Incorrect**
**Option A:** Vitiligo - While a Wood's lamp can be used to assess the pigmentation of the skin, it is not a primary tool for diagnosing vitiligo.
**Option B:** Eczema - Eczema is a broad term for a group of skin conditions characterized by inflammation and itching, and a Wood's lamp is not a diagnostic tool for this condition.
**Option C:** Psoriasis - While a Wood's lamp can be used to assess the skin in patients with psoriasis, it is not a primary diagnostic tool for this condition.
**Clinical Pearl / High-Yield Fact**
When using a Wood's lamp, it's essential to note that the fluorescent light can be affected by the presence of certain medications, such as tetracyclines, which can cause a false-positive result.
**Correct Answer: D. Fungal and bacterial infections.