Product Spotlight: Woods Lamp Replacement Bulb

Bessy the cat and Walter the kitten

Blacklights are not merely for special effects and lighting up cool posters. They also have an important clinical use: diagnosing ringworm in cats, dogs, and other animals. The most common tool veterinarians use to diagnose ringworm on pets is a Woods Lamp, which is another name for the common blacklight bulb.

According to Wikipedia, Woods lamps have been used since 1925 to detect fungal infections in hair. The fungus that causes ringworm fluoresces under the ultraviolet light from the blacklight. By shining patches of skin and fur under the UV light, vets can see the fungus.

Fluorescence is a colored glow that is emitted by a substance that absorbs light or electromagnetic radiation from an outside source. As the fungus absorbs the ultraviolet light from the blacklight, it emits a color in response. Using light is a simple way to detect ringworm, although not the only way. The color of ringworm under a Woods Lamp is a bright apple green, which may show under a blacklight with a blue filter in a darkened room.

It should be noted that, according to PetMD, not every case of ringworm can be diagnosed with a blacklight, as some types of fungi do not fluoresce. If you suspect a fungal infection in your pet, always seek proper veterinary care.

Although blacklights can have no filter, the more widely recognized version has a dark blue filter. This blocks out most visible light. That brings us to our featured product of the week, a common replacement blacklight bulb for Woods lamps.

The F4T5 blacklight blue bulb has a peak wavelength of 368nm and a total UV output of 0.5 watts. True Woods lamps fluoresce at this ~360nm wavelength, according to Shelter Medicine, which also advises against using a generic ultraviolet light in the tool. Topbulb also stocks a wider array of blacklight replacement lamps, including in many different sizes and wattages. We also carry UV-A blacklight bulbs with no filter for other common lighting applications.

F4T5/BLB Key Features:
blacklight blue light bulb

The F4T5 blacklight bulb with dark blue filter

  • 130 volts, 4 watts
  • Fluoresces at wavelength of true Woods lamps
  • Used as inspection tool by vets and medical professionals
  • Blue coating prevents emission of most visible light
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Nick Heeringa

Nick is a writer, publisher and editor for the Topbulb blog. Check back often for more of his writing on lighting applications and announcements for the Topbulb website and blog!