sunscreen Flashcards
What are the ideal properties of sunscreen?
absorption of harmful uv radiation (280-360nm), nontoxic, non-staining, odourless, chemically stable, inert, pure, waterproof
What does SPF measure?
it measures the effectiveness of sunscreen against UVB rays
How is SPF tested on the skin?
we apply a uniform layer of sunscreen on the skin (2 mg/cm^2). MED (minimal erythemal dose) is tested - how long it takes for the skin to turn slightly red with and without sunscreen which can be ratioed to give SPF
What does “broad spectrum” mean in terms of sunscreen protection?
≥ 15 and protection against UVA protection (that meets a certain criteria)
What is the wavelength range for UVA protection?
(320-360 nm)
List the factors that affect the effectiveness of sunscreen.
- when u apply it
- how much is applied
- formulation
- waterproof
- product’s age and expiry date
How do physical absorbers like ZnO and TiO₂ protect the skin from UV rays?
scatter, reflect and absorb sunlight
What is the difference between nanoparticles, microfine, and fine particles in sunscreens?
Nanoparticles (<100 nm): Absorb and scatter UV rays, can penetrate damaged skin.
Microfine particles (80-120 nm): Block UVB to 330 nm and are cosmetically acceptable.
Fine Particles (>200 nm): Block both UVB and UVA but are less cosmetically acceptable.
How do chemical absorbers work, and can you name some examples?
absorbs sunlight and dissipates it as heat energy.
examples include: Cinnamates, aminobenzoic acid derivatives, benzophenones.
What is urocanic acid, and how does it protect the skin from UVB radiation?
Urocanic acid is a natural sunscreen derived from the amino acid histidine. It absorbs UVB rays, converting from its trans form to the cis form upon exposure to UVB light. Afterward, it spontaneously reverts back to the more stable trans form. This allows it to protect the skin by absorbing UVB radiation.
What is BEMT, and why is it considered effective and safe for broad-spectrum protection?
a broad-spectrum sunscreen agent that protects against both UVA and UVB rays
- It doesn’t easily penetrate the skin, reducing toxicity.
What is phototautomerism, and how does it relate to BEMT?
When exposed to light, it undergoes a temporary chemical change where protons shift within the molecule making it more effective in absorbing and blocking UV radiation. The chemical change is brief and doesn’t cause harmful skin reactions.
What are Sunspheres, and how do they improve sunscreen effectiveness?
These are hollow, inert polymer spheres that reflect and scatter UV light. They enhance the effectiveness of active UVA/UVB ingredients by 50-70%.
What are Eusolox Pearls, and what are their key benefits?
These are microencapsulated sunscreen ingredients. Benefits include:
Reducing absorption into the skin.
Improving photostability (more stable under sunlight).
Allowing the combination of ingredients that might otherwise be incompatible.
