What is Sun Protection Factor?
When shopping for a sunscreen, consumers are faced with many choices. These choices include the sun protection factor (SPF) rating, which can vary from 8 to 50.
SPF is a measure of how much sunlight (UV radiation) is needed to develop sunburn after a sunscreen has been applied, compared to the amount of UV radiation required to develop sunburn on unprotected skin. The higher the SPF, the greater the protection is from UV radiation, and so the greater the sunburn protection.
It is important to know that SPF does not tell you how long you can be in the sun without getting sunburn. SPF does not mean that if you normally burn in 1 hour and you apply an SPF 8 sunscreen, it will take 8 hours for you to burn. Wrong. Instead, SPF tells you the amount of sunburn protection from UV radiation that is provided by sunscreens when they are used as directed – not burn protection time.
Several things can affect the amount of UV radiation exposure:
- time of day
- geographic location
- altitude, and
- weather conditions (cloudy day versus clear)
For example, a person spending 15 minutes in the sun at noon in Boston without sunscreen may not sunburn, but that same person could burn after spending 15 minutes in the sun in Miami because of the higher amount of UV radiation exposure in the geographic location.
Skin complexion, amount of sunscreen applied, and how often you reapply can also affect exposure. In order for a sunscreen to be effective, it’s important that it be applied as directed, and reapplied as directed and needed based on physical activity. Participating in activities like swimming or activities that can promote heavy sweating may require more frequent reapplication.
Remember, SPF does not tell you how long you can be in the sun without getting sunburn. Instead, it’s a measure of the amount of sunburn protection from UV radiation that is provided by sunscreens when they are used as directed and as needed.
Fun in the sun can be had all year long -- hiking, winter skiing, swimming, or just enjoying the warmth of the sun. However, when taking certain medicines, life in the sun can sometimes be less than fun.
Some medicines contain ingredients that may cause photosensitivity -- a chemically induced change in the skin. Photosensitivity makes a person sensitive to sunlight and can cause sunburn-like symptoms, a rash or other unwanted side effects. It can be triggered by products applied to the skin or medicines taken by mouth or injected.
There are two types of photosensitivity – photoallergy and phototoxicity.
Photoallergy is an allergic reaction of the skin and may not occur until several days after sun exposure. Phototoxicity, which is more common, is an irritation of the skin and can occur within a few hours of sun exposure. Both types of photosensitivity occur after exposure to ultraviolet light – either natural sunlight or artificial light, such as a tanning booth.
There are certain types of medicines that can cause sensitivity to the sun. Some of these include:
- Antibiotics (ciprofloxacin, doxycycline, levofloxacin, ofloxacin, tetracycline, trimethoprim)
- Antifungals (flucytosine, griseofulvin, voricanozole)
- Antihistamines (cetirizine, diphenhydramine, loratadine, promethazine, cyproheptadine)
- Cholesterol lowering drugs (simvastatin, atorvastatin, lovastatin, pravastatin)
- Diuretics (thiazide diuretics: hydrochlorothiazide, chlorthalidone, chlorothiazide.; other diuretics: furosemide and triamterene)
- Non-steroidal anti-inflammatory drugs (ibuprofen, naproxen, celecoxib, piroxicam, ketoprofen)
- Oral contraceptives and estrogens
- Phenothiazines (tranquilizers, anti-emetics: examples, chlorpromazine, fluphenazine, promethazine, thioridazine, prochloroperazine)
- Psoralens (methoxsalen, trioxsalen)
- Retinoids (acitretin, isotretinoin)
- Sulfonamides (acetazolamide, sulfadiazine, sulfamethizole, sulfamethoxazole, sulfapyridine, sulfasalazine, sulfasoxazole)
- Sulfonylureas for type 2 diabetes (glipizide, glyburide)
- Alpha-hydroxy acids in cosmetics
Not all people who take or use the medicines mentioned will have a reaction. Also, if you experience a reaction on one occasion, it does not mean that you are guaranteed to have a reaction if you use the product again.
If you have concerns about developing a reaction, try to reduce your risk:
- When outside, seek shade, especially between 10 a.m. and 2 p.m. – some organizations recommend as late as 4:00 p.m. Keep in mind that the sun’s rays may be stronger when reflected off water, sand and snow.
- Wear long-sleeved shirts, pants, sunglasses, and broad-brimmed hats to limit sun exposure.
- Use a broad sunscreen regularly and as directed. Broad-spectrum sunscreens provide protection against ultraviolet A (UVA) and ultraviolet B (UVB) radiation. An SPF 15 is the minimum number needed to provide measurable protection; however, a sunscreen with an SPF value of 30 or higher is recommended. Rarely, some sunscreen ingredients can cause photosensitivity themselves.
If you have questions about your medications and the possibility of a photosensitivity, contact your health-care professional or pharmacists. Taking a few precautions can help limit your risk of photosensitivity and keep the sun shining on your fun.
How does sunlight affect medication? ›
Sunlight delivers a heavy dose of ultraviolet (UV) rays, which in some cases could interact with medication in your body and increase the risk of sunburn, rash or heatstroke. “Certain medications contain ingredients that may lead to a chemically induced change within the skin,” says Alyssa Wozniak, PharmD.What medications should you avoid the sun? ›
There are certain types of medicines that can cause sensitivity to the sun. Some of these include: Antibiotics (ciprofloxacin, doxycycline, levofloxacin, ofloxacin, tetracycline, trimethoprim) Antifungals (flucytosine, griseofulvin, voricanozole)Why can't you sit in the sun when taking antibiotics? ›
Unfortunately yes, there is a connection between antibiotic treatment and sun sensitivity. Some antibiotics (and other medicines) can make you more sensitive to sun exposure. This can cause sun burn and rashes more easily than you normally expect.Should a person stay out of the sun if they are using a medication that says photosensitive? ›
If you have photosensitivity, you may develop a rash after being in the sun, as well. There are many possible reasons photosensitivity happens. But medications can be a common culprit. If your medication has a warning to avoid sunlight or mentions photosensitivity as a possible side effect, don't ignore it.What medications react to the sun? ›
- Coal Tar and Derivatives.
- Contraceptives, Oral and Estrogens.
- Non-Steroidal Anti-Inflammatory Drugs.
Among heat-interacting medications are antidepressants, antihistamines, antipsychotics, and diuretics (detailed below). Unfortunately, many who prescribe these drugs, as well as those who dispense and those who use them, may be unaware of the risk presented by their use under conditions of extreme heat.What blood pressure meds make you sun sensitive? ›
Blood-pressure medications that are often referred to as "water pills", such as hydrochlorothiazide and furosemide (also known by the brand name of Lasix), can make your skin more likely to experience sun sensitivity.When should you avoid the sun? ›
Seek shade: Limit your direct exposure to the sun, especially between 10 a.m. and 4 p.m., when UV rays are strongest. Cover up: When you are out, wear clothing and a wide-brimmed hat to protect as much skin as possible.Why do medications cause sun sensitivity? ›
Drug-induced photosensitivity is an adverse skin reaction induced by sun exposure in some patients taking particular medicines1. As the skin absorbs ultraviolet (UV) radiation this can cause a chemical change to a medicine that is present in the skin resulting in a phototoxic or photoallergic reaction2.Why can't you lay down after taking some antibiotics? ›
Do not lie down immediately after taking medicine, to make sure the pills have gone through the esophagus into the stomach. Notify your healthcare provider if you experience painful swallowing or feel that the medicine is sticking in your throat.
Can sunlight or heat affect medication? ›
Both excessive heat and cold can have significant impact on how well medication — both prescription and over-the-counter — do their job.Is it OK to be in the heat while on antibiotics? ›
Erdos said. “Other medications like anticholinergics, such as Benadryl or diphenhydramine, acne medications, amphetamines, antidepressants, antibiotics and several others can increase your risk of overheating and make you more sensitive to the sun.”What happens if you spend too much time in the sun on antibiotics? ›
Lipman, M.D. For example, taking the antibiotic doxycycline and going out in the sun could increase your risk of developing painful or itchy rashes that lead to blistering. Other antibiotics can cause you to sunburn much more quickly.What are symptoms of photosensitivity? ›
Symptoms of photosensitivity may include a pink or red skin rash with blotchy blisters, scaly patches, or raised spots on areas directly exposed to the sun. Itching and burning may occur and the rash may last for several days. In some people, the reaction to sunlight gradually becomes less with subsequent exposures.What are the symptoms of phototoxicity? ›
In phototoxicity, people have pain and develop redness, inflammation, and sometimes brown or blue-gray discoloration in areas of skin that have been exposed to sunlight for a brief period.Does sun affect antidepressants? ›
Hundreds of medications affect photosensitivity, expert says
“They include some diuretics, antibiotics, antihistamines, anti-arrhythmics, antiseizure medicines, acne medications, and antidepressants. Most of the photo reactions are caused by the ultraviolet (UV) A and UVB rays and usually present as an allergy.
A patient's lifestyle habits may be interfering with medications. Negative lifestyle factors such as excess weight, smoking, physical inactivity, and binge drinking can affect the health of patients taking certain medications.How long does sun sensitivity from antibiotics last? ›
Photoallergic reactions often result in blisters, redness, a rash, and oozing areas of skin that lasts for up to two weeks. Indicators of a phototoxic reaction can vary from symptoms like skin irritation and pain to localized swelling.