The Deets on Sun Damage
Sunshine and clear skies ahead! Which means it is time to up our sun protection game. Daily prevention of sun-induced skin damage is part of any healthy skincare routine - and even more important as the UV index goes up and we spend more time outside. Confused by UV levels? Wondering what types of skin damage occur from sun exposure? How to treat a sunburn? Read on for all the answers!
Ultraviolet (UV) Radiation
Both immediate (acute) and long-term (chronic) exposure to UV radiation damages the skin. Regardless of skin colour, everyone will burn with large doses of UV radiation. UV exposure is linked to 90% of non-melanoma skin cancers and 65% of melanomas. More than likely, you’ve heard that UV radiation is strongest between 10am and 4pm and at higher altitudes. This radiation is increased by reflective surfaces (eg concrete, sand, snow), high temperatures, air pollution, humidity, and wind.
The UV index is reported by Environment Canada, and predicts the daily strength of ultraviolet rays (reporting indices of 3 or above), with a higher UV reading meaning higher sunburn risk (see the chart below).
UV light has 3 categories: UVA, UVB, and UVC. UVA radiation is present all day, and can penetrate through windows, clothing, and water; it’s dangerous because it goes deep into the dermis (the second layer of skin) and even to subcutaneous fat (the third layer of skin). It can impair normal cell, blood vessel, and collagen functions, creating reactive oxygen species that contribute to the destruction of proteins and nucleic acids, the building blocks of DNA. Although UVA is a less potent carcinogen than UVB or UVC, more UVA reaches Earth than the other types so it significantly contributes to skin cancer risk. It is also the cause of phototoxic drug eruptions, as well as immunosuppression, epidermal thickening, decreased skin barrier function and photoaging. While UVB radiation doesn’t penetrate the skin as deeply as UVA, it is the main cause of sunburn. Even at low doses, it can cause direct DNA damage, skin abnormalities, and immunosuppression. It is estimate that a 1% decrease in ozone leads to a 1.5% increase in UVB, which means a 2-6% increase in basal and squamous cell cancers, and a 0.3-2% increase in melanomas - so risk will only increase as the ozone layer thins. UVC radiation is filtered by the surrounding ozone layer and currently doesn’t reach the earth’s surface.
Skin Damage due to Sun Exposure
Sun-induced skin damage occurs in all skin colours and can be acute or chronic. It can also make certain conditions, such as lupus, rosacea, and melasma, worse. Pigmentation (eg tanning) does not occur without damage or death of epidermal cells, and does not protect against DNA damage.
Acute Skin Damage
Did you know that the typical sunburn is actually an inflammatory response of the skin to UV radiation? The redness usually occurs 2-6hrs after exposure to UV radiation, and starts to subside within 72-120 hrs. Usually, swelling, pain, itch and redness are present, and in severe cases blistering can occur. Other symptoms can include nausea/cramps, fever, chills, weakness, headache, and generally feeling unwell.
In patients taking certain medications, sun exposure can result in a phototoxic drug eruption. This is a chemical reaction that appears like a sunburn, within minutes to hours after sunlight exposure. The reaction is usually only on exposed skin, and is mostly due to UVA radiation. Check out my instagram post for specific medications that can cause this eruption.
Another photosensitive disorder called polymorphous light eruption (PLE) is common, likely due to genetics and environment. Usually it occurs within hours of UV exposure, and appearance can vary - often it looks like a rash or groups of itchy pink/red bumps.
A small number of patients might have a delayed hypersensitivity reaction (an allergic reaction that doesn’t occur immediately) - called a photoallergic reaction - after sunlight exposure. This usually starts 1 to 3 days after sun exposure, and can extend beyond the specific area that was exposed. Another rare condition called solar urticaria can cause hives after being exposed to the sun, occurring within minutes of exposure and lasting for hours.
Chronic Skin Damage
Continuous, long-term sun exposure leads to skin damage in the following categories:
Dyspigmentation includes freckles (often appearing during childhood in fair skinned individuals) and age spots or “liver spots” (appearing later in life) due to UV radiation exposure.
Photoaging is basically premature skin aging. Skin becomes rough, leathery, coarse, and dull, with both fine and deep wrinkles, often due to a change in skin glycosaminoglycans which normally help retain water. Photoaging also includes telangiectases (e.g. spider veins) and easy bruising due to blood flow changes in the dermis.
Actinic keratoses are pre-cancerous lesions more common in males and light-skinned individuals, usually appearing after 50 years of age. These can be firm, scaly, slightly red lesions, which untreated may progress to squamous cell carcinoma.
Keratinocyte skin cancer, previously called “non-melanoma” skin cancers, include both squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). SCC risk is related to cumulative lifetime sun exposure, often on face, ears, and neck, as well as forearms and back of hands and legs. Initially the lesion may be scaly/crusty or raised, and may bleed or erode over time. BCC is related to episodes of sun exposure during childhood/adolescence, and are commonly found on the face. Usually these are small, dome-shaped lesions with a shiny surface that slowly enlarge.
Melanoma skin cancer is less common, but is more serious and related to intense, sporadic sun exposure as a child/adolescent. Risk increases with persistent sun exposure, family history, sunburn history, and those who tan poorly and burn easily. Usually starting as a flat brown/black spot (or a mole) with irregular edges, it may enlarge if left untreated. See the image below for the ABCDEs on how to evaluate a mole - any suspicious spots should be seen by a doctor right away.
Image retrieved from Baptist Health: https://share.baptisthealth.com/mole-or-melanoma-5-signs-of-skin-cancer/
Preventing Skin Damage from Sun Exposure
The basics are pretty simple and self explanatory[1,2]:
Avoid direct sunlight, especially between 10am and 4pm
Be aware of when the UV index is high
Find shade as much as possible
Wear sun-protection clothing with UV protection factor (UPF) labelling (25-35 considered very good, >50 excellent protection)
Cover up with lightweight long-sleeved shirts or pants
Wear tightly-woven wide brimmed hats (long term use may reduce skin cancer risk by 40%!)
Protect eyes from cataracts and eye cancer with 100% UV protection sunglasses
Umbrellas help reduce UV radiation, but do not protect against reflected radiation
Wear sunscreen appropriately
Be especially careful about sun exposure while on medication
Keep children under 6 months in the shade and covered
Do not use artificial tanning beds
It’s also important to be aware that wet, white, or loosely woven clothing offers little protection from UV rays, and that all the above should be used for prevention - wearing sunscreen is an additional protective measure, don't rely on it alone! No sunscreen provides complete protection from the sun. Choose a broad-spectrum sunscreen with an SPF of at least 30 (see this complete post on sunscreen).
Treating Skin Damage from Sun Exposure
Sunburn. Alas, despite your best efforts, you have a sunburn. Make sure to drink plenty of water to prevent dehydration and avoid any further sun exposure for at least 1 week[1,2]. A cool compress, which is a soft cloth soaked in cool water, on and off the affected area may help relieve pain. Inflammation usually occurs in the first 24 hours, when an anti-inflammatory (such as ibuprofen, a.k.a. Advil) may be helpful - but check with your pharmacist first! If blisters are present and severe, it should be treated as a burn and may require proper wound care. Once the burn is no longer hot, if friction from clothing causes irritation, an occlusive or emollient may help with redness, protect the area, and moisturize the dried skin (with something such as petrolatum or mineral oil). Some people find aloe gel cooling and soothing.
Photoaging. Skincare products with retinol have limited effects on photoaging, as concentrations are too weak. Antioxidants (vitamin C, CoQ10) allegedly improve photoaging signs. Currently, compounds such as peptides, ginseng, green tea polyphenols, isoflavones, lutein, and carotenoids are being studied for reversing signs of photoaging. AHAs (glycolic and lactic acids) may help reduce appearance of minor photodamage (improving fine lines, firmness, and tone). Hydroquinone (only available on prescription in Canada) can help lighten darkened skin, while topical retinoids (tazarotene, adapalene, tretinoin) can reduce wrinkle appearance and increase smoothness of skin. Other options for photoaged skin treatment include laser resurfacing, microdermabrasion, and chemical peels to even skin tone.
So what do you think? Do you still have any sun safety questions? Let me know! And relating to sunscreen - I have an entire post dedicated to this, which you can check out here. Stay sun safe!
Kleiman, N. Prevention and Treatment of Sun-Induced Skin Damage. Canadian Pharmacists Association. Revised April 12, 2021. Retrieved 25May2021 from eCPS.
Guenther, L. Sunburn. Canadian Pharmacists Association. Revised February 19, 2019. Retrieved 25May2021 from eCPS.
Baptist Health. Mole or Melanoma? 5 Tips for Detecting Skin Cancer. August 7, 2020. Retrieved 27May/21 from https://share.baptisthealth.com/mole-or-melanoma-5-signs-of-skin-cancer/.
DISCLAIMER: The contents of this blog are for educational purposes and are not intended as medical advice. I enjoy researching but the information is general and not comprehensive. Please seek the advice of your healthcare provider (pharmacist/physician etc) with any questions you may have regarding your personal health. Never disregard professional medical advice or delay in seeking it because of something you have read online. Any mention of specific products or personal recommendations are my opinion and not to be taken as medical advice.