For many years now, we at the JAEH have been concerned with the limited management options for pets that have no melanin pigment in their eyelids, noses and ears. The incidence of squamous cell carcinoma is rather high in this group of pets and for this reason, we are consistently looking for alternative treatment options. Recently published information appears to suggest that tattooing may have a beneficial effect.
We are pleased to announce that this is a new treatment option that will be provided by our hospital.
Skin Cancer & Eyelid Tattooing in Animals
This information leaflet is designed to present a scientific and objective view of current information regarding the presence of skin cancer in animals and tattooing with black ink as an option that could assist in reducing the chance of skin cancer in pale skinned animals.
Many of our domestic pets are born with no dark melanin pigment around their eyelids, noses and ears and this frequently leads to serious pathology as a result of sun damage. All breeds with pale and pink skin such as Jack Russell Terriers, Fox Terriers, Bull Terriers, Maltese and white cats, for example, are at high risk for developing skin cancer. Horse breeds such as the Appaloosa and Palomino are also at risk. Melanin pigment in the skin protects against solar damage by absorbing visible and ultraviolet [UV] light and serves as a direct free radical scavenger.
Understanding the Effects of Ultraviolet Light on the skin:
Cat: SCC of the eyelids
1] UVA rays penetrate the skin by about 1.5mm and cause increased stimulation of the pigment-producing cells in the skin, called melanocytes. The melanin pigment produced by these cells absorbs the radiation into the cells of the skin or eyelid in animals that have these cells. This pigment forms a protective barrier preventing the UV light from reaching and damaging deeper lying cells.
2] UVB causes intense damage to the outer skin layer called the epidermis, resulting in sunburn, inflammation, ageing changes and most importantly leading to a type of skin cancer termed squamous cell carcinoma [SCC]. [In man the common tumours are basal cell carcinoma, SCC and melanoma]
3] UVC type of radiation is the most destructive, but fortunately, is absorbed in the ozone layer around the earth.
UVA and UVB mainly contribute towards skin damage when no or reduced melanin pigment is present in the skin. Normally pigmented eyelids have melanin-containing cells. Melanin is a pigment that absorbs the energy of the UVA and UVB light and helps filter these rays, thus reducing the damage to the outer skin layers. When there is reduced melanin in the skin or eyelid, the strong UV rays can harm the cells. The result is that blood vessels in the deeper skin layers dilate, turning the skin and eyelid very red and giving it a nasty inflamed appearance. When eyelids and other periocular tissues are affected, the diagnosis of solar blepharitis is made.
The sun’s rays damage the DNA of the cell and these damaged cells then form large numbers of identical cells which have a rapid rate of cell division. Pre-cancerous cells are actually formed when animals are young, and only later, with continued sun exposure, do we see the evidence of Squamous Cell Carcinoma [SCC].
The typical SCC undergoes three definite stages starting with inflammation of the skin characterised by a raised red, inflamed area of skin. If the eyelid is involved this frequently forms scabs, which can slough off and bleed or ulcerate. This stage progresses to the carcinoma in situ which is also red, raised and ulcerated and on biopsy, one would see definite damage to the deeper, dermis layer of the skin. The final stage is the true squamous cell carcinoma, which, on biopsy shows cords of cancerous cells invading the deep layers of skin. Should cancer reach the bone of the orbit, the prognosis is zero.
It has also been shown that the incidences of these skin changes are more severe in areas that have high levels of sunshine and high altitude over 1000m. Gauteng experiences some of the highest UV radiation levels in the world.
Skin and Eyelid Cancer:
Skin cancer or tumours can result from the damaging effects of UV rays. The mechanism of action of skin cancer has been shown to be related to the formation of pyrimidine dimers in the DNA of cells. Incoming UV light energy will damage the thymine or cytosine bases in the DNA and in some cases, two consecutive bases bind forming a dimer. These dimers then interfere with further normal base pairing replication of the DNA and can then lead to mutations of cells which subsequently form cancer. Fortunately, our bodies can try and deactivate these and cause repair of these bonds but any unrepaired dimers then become mutagenic and these are the primary causes of melanoma skin cancers in humans .
These are labelled with an SPF or “Sun Protection Factor”. This is a relatively standardised rating. For example, if the skin begins to burn after 10 minutes of exposure, a comparable burn will take 15 times as long when it is protected with an SPF15 sunscreen. There are many products on the market, but most seem to irritate the pet’s eye when applied to the delicate skin of the eyelid.
We recommend that a small amount of a non-irritable cream can be applied to your finger and then smeared liberally onto the eyelid including the eyelid margin which has no hair. In summer, or if the pet spends much of its time in the sun, then this should be done on a regular basis during the day, as one would do if sunbathing around the swimming pool. The product can also be applied to other susceptible areas of the body such as the nose, ears, abdomen and scrotum.
Historically the concept of merely infiltrating the dermis with a dark ink pigment does not actually simulate the function of melanin in the cells of the skin which has resulted in the concept of tattooing pale skin being very controversial. Current information may suggest otherwise.
In Germany over 10% of the population has tattoos and this is higher in some other nations. Over 80 million Americans have tattoos. Following an intensive literature search, it appears the incidence of skin cancer in the darkly pigmented tattooed skin is very rare in people compared to the vast numbers of people with tattoos. A recent Danish journal article  has shown that mice, that were tattooed with black tattoo ink, were better protected against UV radiation [UVR] induced malignant skin cancer [SCC’s] when compared to fellow non–tattooed mice that were also exposed to the same radiation. All mice, however, developed skin cancers during the study period but the development of skin cancers in the tattooed and irradiated group was significantly delayed and less extensive than the non-tattooed group. Sophisticated equipment was used to take skin reflective measurements, and these indicated that the protective effect of black pigment in the dermis might be attributed to UVR absorption by the black tattoo pigment below the epidermis and thereby reduction in backscattered radiation that could be damaging the tissues leading to skin cancer.
At the Jhb Animal Eye Hospital we are also not naïve about the negative information regarding tattooing and thus feel it is important to mention this. The black ink pigment used by tattooists around the world varies in quality and active ingredients. Most black pigments are carbon-based, soot products and may contain polycyclic aromatic hydrocarbons [PAH]. These are ubiquitous chemical pollutants and originate from incomplete combustion of fossil fuels, pyrolysis of organic material, vehicular emission, petroleum catalytic cracking, residential wood burning and cooking [“braai-ing” of meat!!]. Intense research has been done and is ongoing to try and establish if tattoo inks with PAHs, in fact, induce skin cancer. The PAHs and the black pigment remain in the skin and some may travel to the regional lymph nodes. It has been shown that the PAHs in the ink can absorb UV radiation and potentially generate a singlet oxygen radical during exposure of tattooed skin and these may be mutagenic or carcinogenic. Although this process has been described it does not seem to deter the millions of people with tattoos and in fact, these negative effects of the PAHs may be negligible as seen by the low incidence of cancers in tattooed skin areas. It is unknown so far, whether PAHs in black tattoo inks can contribute to any carcinogenic risk for tattooed humans . It is difficult to compare the risk of tattooing to other routes of administration of PAHs such as inhalation and dietary intake. The pigment and PAHs predominantly stay in the skin as well as some can be noted in the regional lymph nodes for life. A dog receiving a tattoo will live much shorter than a human and most likely will not have the chronic exposure and potentially negative effect that is speculated in people. The research on this topic is particularly important, however, for trying to establish a safe standard of tattoo inks with low amounts of PAH’s and the least toxic types. The tattoo ink used at the Jhb Animal Eye Hospital [JAEH] is an EU rated and accepted ink that has been shown to have extremely low levels of PAHs .
The Johannesburg Animal Eye Hospital is now offering tattooing of non-pigmented tissues in domestic pets [eyelids, ears, noses etc.] as a means of trying something to assist these patients. As mentioned, melanin pigment protects against solar damage by absorbing visible and UV light and serves as a direct free–radical scavenger. Black tattoo ink absorbs all visible light rays [from 380-740nm] and could absorb UV waves . The reports of 2010 and 2012 indicated that there is no current definitive evidence to show that the ink itself absorbs or protects against UV light damage. It is the Danish study of 2015  that is the most encouraging and they concluded that based on their skin reflectance measurements it indicates that the protective effect of black pigment in the dermis might be attributed to UVR absorption by black pigment below the epidermis and thereby reduction of backscattered radiation that seems to assist in reducing the extent of skin cancer formation. Based on this recent knowledge we are going to offer prophylactic tattooing of pets' eyelids. We acknowledge that there is no further current research information available that we are aware of and no known studies in dogs and cats have been conducted as far as we know. We will continue to monitor current research in this field and amend our approach as deemed necessary.
It is extremely important to note that the tattooing will be performed using the most modern and sophisticated electronic tattoo guns that are available and only high-quality pigments and consumables will be used. We will consistently monitor tissue reactions or sensitivities to products and we encourage owner compliance and assistance in this regard.
We propose that interested pet owners consent to this elective procedure and that the data will be collected and the patient monitored over time and hopefully we can learn a lot more about the potential protective ability of tattooing.
After the tattooing procedure, as is the case with people receiving tattoos, there are some very specific and important treatment principles that need to be obeyed. We shall endeavour to use a protective plastic collar to prevent the pet scratching or a face mask in the case of horses. The tattoo needle has obviously entered the skin to deposit the ink in the deep dermis and this skin may go through an inflammatory process and this may result in the tattooed skin being swollen, red, ooze serum and even form a bloody type crust. This may persist for a few days or weeks. During this phase, you will be required to use a protective and soothing Beeswax preparation to keep the skin soft, healthy and clean. Do not wash the area or allow the pet to swim. Like people, there may be a wide variation of the extent of post-tattooing inflammation. Oral anti-inflammatories will also be used. A check-up appointment will also be required about 10-14 days after the tattooing.
- Lerche C, Black tattoos protect against UVR-induced skin cancer in mice. Photodermatology, Photoimmunology & Photomedicine, 2015, 261-268
- Fig 1: https://earthobservatory.nasa.gov/Features/UVB/
- Regensburger J, Lehnr K, Tattoo inks contain polycyclic aromatic hydrocarbons that additionally generate deleterious singlet oxygen. Experimental Dermatology, 2010, 19 275-281
- Lehner K, Analysis of black tattoo inks: Ingredients, Interaction with Light, and Effects on Cellular Systems, Dissertation, 2012
- Gionfriddo J, Tattooing of the Equine Eyelid: a Retrospective Study. 2009, Journal of Equine Veterinary Science 29, 2 82-86