Sunscreen (Wk 1 PhPPC)

Skin Care I & II

Sunscreen and Sun Tan Products

Ultraviolet Radiation

• UV Spectrum Ranges: 200-400 nm

• Divided into 3 Bands:
    - UVC
    - UVB
    - UVA

• Wavelength Breakdown:
    - UVC: 200-290 nm
    - UVB: 290-320 nm
    - UVA: 320-400 nm

UVC Band

• Characteristics:
    - Little of this band reaches the Earth's surface due to the ozone layer, which screens it out.
    - Deviates from natural sunlight, UVC is emitted by artificial sources such as mercury lamps.

• Effects on Skin:
    - Absorbed by the dead cell layer of the epidermis.
    - Does not stimulate tanning but can cause some redness.

UVB Band

• Also Known As: Sunburn radiation

• Effects:
    - Causes the typical sunburn reaction and stimulates a slow tanning process.   - Associated with sun damage and increases risk for certain skin cancers.
    - Most erythrogenic and melanogenic of the three UV bands.
    - Small amounts are necessary for normal Vitamin D synthesis in the skin.

UVA Band

• Characteristics:
    - Slightly blocked by the ozone layer; however, it reaches the Earth's surface in amounts 10-100 times greater than UVB.
    - Penetrates deeply into the skin but does not cause sunburn.
    - Cannot be measured using SPF testing, as there is no reliable clinical measurement for UVA blockade.

UVA Effects

• Usage: Often utilized in tanning booths because it delivers a rapid tanning effect.

• Negative Effects:
    - Responsible for numerous photosensitivity reactions, photoaging (skin aging due to UV exposure), and photodermatoses.
    - UVA penetrates deep into the dermis, amplifying the cancerous effects of UVB rays through indirect DNA damage (free radicals, reactive oxygen species).
    - Triggers the release of melanin and oxidizes melanin already present in the skin.

Effects of Ultraviolet Exposure

• Skin Conditions and Reactions:
    - Actinic Keratoses
    - Different forms of Skin Cancer:
      - Squamous cell carcinoma
      - Basal cell carcinoma
      - Malignant melanoma
    - Drug-induced photosensitivity reactions
    - Photodermatoses
    - Photo-aging

Factors Affecting UV Radiation Exposure

• Time of Day:
    - Highest exposure to UVB occurs between 10 AM and 2 PM.
    - UVA rays are consistently present throughout the day, contributing to 95% of rays reaching the Earth.

• Environmental Factors:
    - Atmospheric conditions (e.g., haze, smoke) affect UV radiation reaching the skin.
    - Sunburn can happen without direct sunlight due to 60-80% UV radiation penetrating through clouds.
    - Reflection of light from surfaces such as sand, water, and snow can increase UV exposure.

• Altitude:
    - UVB intensity increases by 4% for every 1000-foot increase in altitude.

• Predisposing Factors:
    - Individuals with fair skin and light hair are more prone to sunburn and skin damage compared to darker-skinned individuals.

Sunscreen Types

• Types of Sunscreen Agents:
    - Physical Sunscreens: Reflect and scatter up to 99% of light across both UV and visible spectrum (290 – 700nm).
    - Examples:
      - Titanium Dioxide
      - Zinc Oxide
    - Advantages:
      - Provides protection from both UVA and UVB rays.
      - Offers immediate protection after application.
      - More suited for sensitive skin.

• Disadvantages of Physical Sunscreens:
    - Can have a greasy appearance and may leave a white cast on the skin.
    - May require more effort to spread due to thicker formulations.
    - Could produce visible drips when sweating.
    - Efficacy may decrease if not applied generously.

• Chemical Sunscreens:
    - Absorb specific portions of UV light spectra to prevent it from penetrating the skin.
    - Groups of Chemical Sunscreens: Divided based on spectra of UVR blockage and chemical classification.
    - Advantages:
      - Usually thinner, easier to apply, and requires less product for effective protection.

• Disadvantages of Chemical Sunscreens:
    - Requires about 20 minutes post-application to become effective. (Longer)
    - Increased probability of irritation and stinging due to combined ingredients for broad-spectrum protection.
    - Higher SPF leads to increased irritation risk for sensitive skin types.

Measuring Sun Protection

• Two Methods for Measuring:
    - SPF (Sun Protection Factor)
    - PPD (Persistent Pigmentation Darkening)

SPF

• Definition: The only FDA-accepted marker of a sunscreen's protective capability, measuring UVB protection.

• Measurement:
    - Based on individual’s time to sunburn, expressed in MED (Minimal Erythemal Dose):
    $ext{SPF} = rac{ ext{MED (protected)}}{ ext{MED (unprotected)}}$

• Interpretation of SPF:
    - Represents how much longer a person can stay in the sun without burning compared to unprotected skin.
    - Example: A person who burns in 10 minutes could theoretically last 300 minutes with an SPF 30, but only if the sunscreen is reapplied every 2 hours.

PPD

• Definition: Represents one of several ways to evaluate a sunscreen's capability in the UVA range.

• Measurement:
    - $ext{UVA PF} = rac{ ext{MPD (Protected)}}{ ext{MPD (Unprotected)}}$
    - Where MPD is the minimal pigmenting dose on human skin.

Problems with PPD

• Not FDA-accepted due to various issues:
    - The UVA light source utilized may not realistically represent natural UVA radiation.
    - Application rates vary the results significantly.
    - Variability among human responses leads to data that may not reflect real-world efficacy.

PA Grading System

• Origin: Developed in Asia, not typically found on EU, Australian, or American products.

• Understanding PA Ratings:
    - PPD Protection Factor Ratings
      - 2 to < 4: PA+ (some protection)     - 4 to < 8: PA++ (good protection)     - ≥8: PA+++ (excellent protection)

Sunscreen Selection Guidelines

Important Considerations

• Questions to Determine:
    - Patient's natural skin type
    - Tanning history
    - Time usually spent outdoors

Skin Types & Recommended SPF

• Skin Type I:
    - Always burns easily; never tans (sensitive)
    - Recommended SPF: 15 or more

• Skin Type II:
    - Always burns easily; tans minimally (sensitive)
    - Recommended SPF: 8 - 14

• Skin Type III:
    - Burns moderately; tans gradually (light brown-normal)
    - Recommended SPF: 4 - 7

• Skin Type IV:
    - Burns minimally; always tans well (moderate brown-normal)
    - Recommended SPF: 2 - 3

• Skin Type V:
    - Rarely burns; tans profusely (dark brown-insensitive)
    - Recommended SPF: 2

• Skin Type VI:
    - Never burns; deeply pigmented (insensitive)
    - Recommended SPF: 0-1

Patient Education & Counseling

Timing and Weather

• Direct Sun Exposure: Most dangerous between 10 AM - 2 PM; advisable to avoid exposure during peak hours.

• Common Misconception: Sun damage can occur on cloudy days due to minimal filtering of UV rays, with 60-80% capable of penetrating clouds, while clouds reduce infrared and create a false sense of safety.

Reflection & UV Transmission

• Reflective Surfaces: Sand and light colors can reflect substantial UV radiation, increasing risk of burns even under shade.

• Water: Even fully submerged, up to 95% of UV rays can penetrate the water.

• Wet Clothes: Encourage up to 50% UV transmission through clothing.

Application Guidelines

• Coverage: All exposed areas should be evenly covered, applying 2 mg/cm²; average adult in a bathing suit requires nine portions (each ½ teaspoon).
    - Face and Neck: 1 portion
    - Arms & Shoulders: 1 portion each side
    - Torso: 1 portion each front and back
    - Legs and Top of Feet: 2 portions each side

• Reapplication: Necessary due to effects of perspiration, swimming, sand, and towels.
    - Water-Resistant Label: Indicates SPF preservation after 40 minutes in water or sweating.
    - Very Water-Resistant Label: Indicates SPF preservation after 80 minutes under similar conditions.

Optimum Application Timing

• Best Practice: Apply sunscreen 30 minutes before sun exposure to allow for full penetration and binding to the skin.

• Age Restrictions: Avoid using on infants below 6 months; do not use < SPF 4 on children below 2 years of age.

• Broad Spectrum Importance: Recommend only broad-spectrum products (both UVA & UVB).

Adverse Effects of Ingredients

• Photosensitivity and Contact Dermatitis are more common with PABA and its esters, while other agents may cause similar issues to a lesser degree.

• Recommendation: Discontinue if irritation occurs.

Suntan Products

Types of Suntan Products

• Two Categories:
    - With Sunscreen: These are low SPF sunscreens.
    - Without Sunscreen: Identified by the absence of SPF on the label.

Products with Sunscreen

• Characteristics:
    - Formulated with an oily vehicle that concentrates UV radiation on the skin.
    - Contain reduced concentrations of certain sunscreen agents, leading to lower effective SPF compared to regular sunscreens.

Products without Sunscreen

• Characteristics:
    - Made with oily vehicles focusing UV radiation on skin.
    - No protection against short and long-term hazards of UV radiation.

• FDA Warning:
    - Warning states: “This product does not contain a sunscreen and does not protect against sunburn. Repeated exposure of unprotected skin while tanning may increase the risk of skin aging, skin cancer, and other harmful effects to the skin even if you do not burn.”

Quiz Questions

Example Questions

1. Which of the following rays has the longest wavelength?
     - a) UVA
     - b) UVB
     - c) UVC
   

2. Which of the following statements describes UVB rays?
     - a) Penetrates deeply but doesn’t cause sunburn
     - b) Is the most erythrogenic and melanogenic
     - c) Gives a quick tan
     - d) Little reaches the surface of the Earth because it is screened out by the ozone layer.

3. Which statement describes titanium dioxide?
     - a) Protects against both UVA and UVB
     - b) Does not leave a white cast on the skin
     - c) Absorbs a UV light spectrum portion
     - d) Spreads more easily on the skin.

4. How many portions of sunscreen should an average adult in a bathing suit apply for adequate protection?
     - a) 5
     - b) 7
     - c) 9
     - d) 11