Ageing skin key points test
Which of the following statements are correct?
# The wavelength range for UVC is 200-320 nm
#! The wavelength range for UVB is 290-320 nm
#! The wavelength range for UVA is 320-400 mm
#! In Auckland in December, UVR is at its greatest at 12:30pm NZST
Explanation: UVR wavebands: UVC (200-290 nm), UVB (290-320nm) and UVA (320-400nm). UVR is at its greatest when the sun is overhead, which is at 12-30 NZ Standard Time or 1:30 Daylight Saving Time.
Effects of UVB include:
#! Genetic mutations
# Immediate pigmentation
#! Phototoxic erythema
#! Proliferation of keratinocytes
Explanation: UVB damages DNA in basal keratinocytes resulting in genetic mutations and protective cellular proliferation. It results in delayed erythema because of the release of inflammatory mediators. Immediate pigmentation occurs in Skin Types 3-6 on exposure to UVA and visible light.
Which skin types have been correctly described?
# Type 1 skin is black and almost never burns
# Type 5 skin is particularly prone to basal cell carcinoma
#! Type 3 skin is olive brown but may burn during summer months
# Type 6 skin is associated with blue eyes and freckles
Explanation: Skin Types are classified according to how easily the skin burns and tans (the fairest, Type 1 to the darkest, Type 6).
The effect of UVR on the normal immune response includes:
#! Cytokine release
# Activation of Langerhans cells
# Histamine release
Explanation: Immune response to exposure to UVA includes cytokine and neuropeptide release, reduction of Langerhans cell function, reduction of histamine release and tolerance.
Chronic effects of UVR may include:
# Dermal thickening
# Seborrhoeic keratoses
Explanation: Chronic effects of UVR (photoageing) changes are dryness (xerosis), skin thinning, pigmentary changes, telangiectasia, easy bruising, solar keratoses and skin cancer. Seborrhoeic keratoses are not considered sun-related, although they may arise in response to injury to the skin including sunburn.
The Sun Protective Factor (SPF) is
#! The ratio of the time for the skin to burn with a sunscreen when exposed to UVR compared without the sunscreen
# A reliable guide to water resistance
# Mandatory to be on the label of sunscreens sold in New Zealand
# Measured in-vitro
Explanation: SPF is measured in vivo. It is the ratio of the time for the skin to burn with a sunscreen when exposed to UVR compared without the sunscreen. Its use is currently voluntary for sunscreens marketed in New Zealand, but it is mandatory in Australia. SPF does not indicate the degree of water resistance of a product.