What ultraviolet wavelength will produce reticuloendothelial stimulation?

• A. 2600-2700 A
• B. 2700-3000 A
• C. 2400-2500 A
• D. 2900-4000 A

Answer: (D)

The wavelength range that stimulates the reticuloendothelial system is in the long-wave ultraviolet, the UVA band, which covers about 2900 to 4000 Angstroms. This UVA light penetrates deeper into the skin and can modulate immune cells such as macrophages, helping to boost activity within the reticuloendothelial system. Shorter UV ranges (the 2400–2500, 2600–2700, and 2700–3000 Angstroms) are more energetic and are largely absorbed by the outer skin layers; they tend to cause direct DNA damage or have strong germicidal effects rather than producing the kind of immune modulation associated with RES stimulation. So, UVA’s deeper penetration and immune-modulating effects make it the best option for stimulating the reticuloendothelial system.