When light causes damage – solar keratoses
Solar keratoses are caused by chronic light damage to the skin from ultraviolet (UV) radiation. They are therefore sometimes also referred to as sun keratoses. This skin change is accompanied by a cornification disorder of the uppermost skin layer, which causes the characteristic appearance of actinic keratoses.
How can solar keratoses be recognized?
Solar keratoses typically appear as reddish or skin-colored, brown or yellowish spots on the skin. When stroked over, they feel rough and scaly (“like sandpaper”). They usually occur on skin areas that are chronically exposed to the sun. These parts of the body are referred to as sun terraces and include the hands, forearms, head and face, décolletage and other light-exposed areas. Often, several light keratoses can be found in one skin area, for example on the scalp.
People with fair skin, people with increased UV exposure (e.g. due to an outdoor occupation), people with a dysfunctional immune system, e.g. due to the use of certain medications, and people over 50 years of age are particularly affected.
It is not yet skin cancer
Light keratoses are considered a precursor to skin cancer. They represent a precursor or very early form of squamous cell carcinoma (also called spinalioma, squamous cell carcinoma) and should therefore be treated by a doctor as early as possible.
Depending on the number of tumors, their size and thickness, their location and the patient’s wishes, surgical removal, cold therapy with liquid nitrogen (cryotherapy), laser therapy and photodynamic therapy (PDT) may be considered.
Squamous cell carcinoma
Squamous cell carcinoma, the second most common malignant skin tumor, usually begins with a thickening of the stratum corneum of the epidermis and then grows into the surrounding tissue, with the edges often inflamed. At the center of the squamous cell carcinoma, there is usually an ulcer with a grater-like palpation finding.
It often occurs at the transition between skin and mucous membrane, e.g. on the lips. It can also develop on scar tissue. The chances of recovery from squamous cell carcinoma are generally good if it is detected and treated early.
The standard medical treatment for squamous cell carcinoma is complete surgical removal. In special cases, radiotherapy is also indicated. If not all of the tumor tissue could be removed during the operation or if more than three lymph nodes are affected, supportive radiotherapy is recommended after the operation (so-called adjuvant radiotherapy).
Solar keratoses usually occur on the so-called “sun terraces”, which also includes the head.
Squamous cell carcinoma begins with a thickening of the stratum corneum of the epidermis.
Skin cancer screening offers early detection of solar keratoses
Skin cancer screening or skin cancer early detection examinations, in which the entire body is thoroughly examined for conspicuous skin changes, are used in particular to detect the preliminary and early stages of skin cancer.
In Germany, anyone with statutory health insurance who is over 35 years of age is entitled to a free skin cancer screening every two years. This can be carried out by a dermatologist. However, other doctors who are qualified to perform this early detection examination (e.g. general practitioners and internists) now also offer this examination.
Some health insurance companies already offer skin cancer screening for those under 35 years of age, so it is worth asking your own health insurance company about this offer. Unfortunately, the offer of skin cancer early detection is currently still not being taken up enough.
Everyone in Germany with statutory health insurance who is over 35 years of age is entitled to a free skin cancer screening every two years.
Prevention is the be-all and end-all
The UV index can be used as a guide to help you assess how much sun protection you need. It can be accessed free of charge on a daily basis, for example, on the website of the German Meteorological Service or via some smartphone apps.
From a UV index of three, sun protection is strongly recommended. In general, in Germany, the intense midday sun should be avoided between 11 a.m. and 4 p.m. from April to September. In addition, shading measures (e.g. sun sails) are generally recommended. This reduces exposure to solar UV radiation.
Personal sun protection measures primarily include the use of textile sun protection (ideally long-sleeved shirts, long trousers and gloves, clothing with a UV protection factor if necessary, and protective headgear with brim, neck and ear protection, as well as closed shoes). It also makes sense to protect the eyes sufficiently with suitable UV-filtering sunglasses. This protection is supplemented by the use of sunscreen products.
Sunscreen products and the like
The cosmetics industry today offers a wide range of different sunscreen products, ranging from creams, gels and lotions to sprays. Generally, the skin type should be considered when choosing a suitable sunscreen: For example, a sunscreen with a higher fat content (e.g. sun cream) can be used for skin that tends to be dry, while oily skin benefits from lighter textures (e.g. sun gel or lotion).
Whenever a part of the body cannot be protected by a textile sunscreen, e.g. the face, a sunscreen should be used. This should be equipped with a broadband filter, i.e. filter both UVA and UVB rays, and have a sun protection factor (SPF) of at least 30, preferably 50+.
Don’t be stingy with the lotion…
To achieve the advertised sun protection factor, a sufficient amount (2 mg/cm²) of the sunscreen must be applied – for the head, face and neck, this is two strips of sunscreen from the tip to the base of the index and middle fingers. Applying too little reduces the protection drastically. Regular reapplication is recommended, about every two hours, and more often if you sweat a lot. After being in the water, the sunscreen should be completely reapplied. Don’t forget your lips either; there are now special lip care sticks with integrated sun protection for them.
Solar keratoses – Caution when working outdoors
The S3 guideline “Prevention of Skin Cancer” (version 2.1, September 2021, registration number 032/052OL) of the Association of the Scientific Medical Societies in Germany (AWMF) names, among others, people who spend a lot of time in the sun as a risk group for developing skin cancer. The occupational group of people who work outdoors is mentioned as an example.
These include, among others, employees in the construction and craft industries, in agriculture and forestry, in fishing and seafaring, and in horticulture. The data showing a doubling of the risk of non-melanoma skin cancer in outdoor workers compared to the average population has led to the recognition of UV-induced skin cancer as an occupational disease in various European countries.
Squamous cell carcinomas, including their early forms, actinic keratoses, can be recognized under Occupational Disease (BK) No. 5103.
Our sun protection tips
– Choose a sunscreen that is tailored to your skin type.
– Always apply sunscreen when a part of your body cannot be protected by a textile sunscreen.
The sunscreen should have a broadband filter, i.e. it should filter both UVA and UVB rays.
The sun protection factor (SPF) should be at least 30, preferably 50+.
To achieve the stated sun protection factor, a sufficient amount (2 mg/cm²) of the sunscreen must be applied. For the head, face and
– For the head, face and neck, apply two strips of sunscreen from the tip to the base of the index and middle fingers.
– Reapply regularly (about every two hours).
– Reapply sunscreen after being in the water.
– Don’t forget your lips either: there are now special lip care products with integrated sun protection and a good flavor.
We recommend high-quality sunscreen products with a high UVA filter content.
Climate change is leading to an increase in terrestrial UV radiation, an increase in cloudless days and thus in hours of sunshine, to negative meteorological influences on the ozone layer in the stratosphere, as well as to so-called low-ozone events and thus to more intense UV radiation in some regions.
The legally required UV-A protection of (only) 30% in relation to UV-B protection is not effective. However, sun protection products are available here for well under 10 euros per bottle. So not much is being invested here and only the legally required minimum is being implemented and offered.
Look for high-quality sunscreen products with a high UVA protection that are advertised by the distributor. However, these products are usually more expensive and start at 15 euros per bottle.
Literature:
Bens G.Adv Exp Med Biol. 2014;810:429-63
Chemical Peels for Skin Resurfacing.
Samargandy S, Raggio BS.2023 Oct 29. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–.
Current therapies for actinic keratosis.
Dianzani C, Conforti C, Giuffrida R, Corneli P, di Meo N, Farinazzo E, Moret A, Magaton Rizzi G, Zalaudek I.Int J Dermatol. 2020 Jun;59(6):677-684
Chen H, Jin S, Zhang J, Luan C, Ju M, Zhang R, Zhang X, Zhu Y, Wang L, Zhuang C, Huang D, Hu Y, Chen K.Photodiagnosis Photodyn Ther. 2024 Oct 10:104363