New type of tattoo ink

Laser tattoo removal is when the pigmented ink in the skin absorbs energy from the laser, breaks down, and is resorbed by the body's immune system. This requires a certain wavelength to target a certain color at a certain depth in the skin. Also, the energy should not be so much as to damage the surrounding skin. Some colors are easier to remove than others, and tattoos that are more skillfully applied at an even depth across the skin are easier to remove as well.

Freedom-2 is an interesting, relatively new product that allows for easier tattoo removal. Instead of the multiple laser treatments and incomplete removal, Freedom-2 advertises tattoo removal after just one laser treatment. They do this by using a biodegradable ink that is microencapsulated. These microcapsules are what make up the tattoo. When a laser's energy is applied to the capsules, they burst, releasing the biodegradable ink. This is assuming it is easier to burst open the capsule than it is to heat and destroy normal ink. Also, it should be easier for the body to dispose of the biodegradable ink than the normal ink.

It is featured as one of Time magazine's best new inventions, and is really a clever idea. However, keep in mind that this product is not FDA-regulated and has not been thoroughly studied in the literature. The material used for encapsulating is not listed on their web page, but it is always a risk that you may have an allergy to the product.

Exercising makes wounds heal faster

At least according to this study. It is a pretty straight forward look at wound size in a sedentary versus exercise group of mice. The exercise did not have a statistically significant effect on wound healing in young mice, but did in older mice. TNF alpha, monocyte chemoattractant, and keratinocyte chemoattractant were all decreased with exercise. These mainly cause inflammation at the wound site. From this data, it can be inferred that exercising reduces inflammation in the skin, which speeds up wound healing in mice. We'll see how this translates to humans, but it's an interesting study overall.

Why is the nose the most common site of BCCs?

A study out of Australia attempts to explain why basal cell carcinomas are most commonly found on the sides of the nose. Here is the news article I found. It seems like a reasonable theory that our curved eyeballs would reflect UV rays onto the side of our noses, making skin cancer more common there than on other parts of our face that are equally exposed to sunlight. Also, the medial canthus (inner corner of the eye) is a common place to see skin cancers, but looks like it is pretty well-shadowed to direct sun. According to this study, it receives a focused ray of UV radiation reflecting from the eye, which might explain its susceptibility to BCCs. The study uses models to show how 60-100% of UV radiation is reflected from the eye surface and where this reflected radiation is eventually absorbed, helping to explain why some areas of the face are more likely to get skin cancers.

Now we need a study discussing the effects of wearing sunglasses on the distribution of skin cancers as the flatter lenses should prevent as much reflection onto the face.

Birt B, Cowling I, Coyne S, Michael G. The effect of the eye's surface topography on the total irradiance of ultraviolet radiation on the inner canthus. J Photochem Photobiol B. 2007 Apr 2;87(1):27-36

Birt B, Cowling I, Coyne S. UVR reflections at the surface of the eye. J Photochem Photobiol B. 2004 Dec 2;77(1-3):71-7.

National Hairdressers Day

Hairdressers are particularly prone to hand dermatitis, and today seems like a great day to discuss why. The constant wet and dry of their hands drys the skin and weakens its protective barrier. With the addition of the large number of irritating chemicals and the possibility of developing allergies to other chemicals, hairdressers have pretty beaten up hands.

PPD (paraphenylendiamine) in black hair dye and glycerol monothioglycolate in hair perming solutions are two allergens that hair dressers come ac. People are exposed to them and over time can become sensitized. This means that the immune system recognizes the chemical as an allergen and mounts an immune response to it upon subsequent exposures.

PPD is also used in "black henna". Henna is naturally green and has not been reported as an allergen before. However, PPD is used to blacken the color, so someone can become sensitized to PPD without having used hair dye. This web page has a great picture of allergic contact dermatitis to black henna (PPD).

Vinyl gloves are effective at preventing PPD sensitization, but not glycerol monothioglycolate sensitization. How do you treat allergic contact dermatitis? Avoidance is the only way to prevent it. And topical steroids can be used to help current lesions heal.

Take home points:
1. Black hair dye, black henna tattoos, and perming solutions contain common allergens
2. People can become allergic to something with repeated exposure over time


Redlick F, DeKoven J. Allergic contact dermatitis to paraphenylendiamine in hair dye after sensitization from black henna tattoos: a report of 6 cases. CMAJ. 2007 Feb 13;176(4):445-6.

Fisher AA. Management of hairdressers sensitized to hair dyes or permanent wave solutions. Cutis. 1989 Apr;43(4):316-8.

CA MRSA in dermatology

Community-acquired methicillin Staphylococcus aureus (CA MRSA) is a relatively recent infection (the last decade). It is particularly relevant to dermatologists as these bacterial strains present most commonly as skin or soft tissue infections. With the recent media blitz surrounding MRSA, it is difficult to discern the medical facts from the news reports. The American Academy of Dermatology has some valuable Talking Points and FAQs that are useful to both patients and healthcare professionals alike.

Mineral makeup

I've heard lots of patients extol the virtues of mineral makeup, and from what I have seen, it appears to be very effective as a natural-appearing foundation. It is pretty amazing how well it covers up patchy skin pigmentation or redness on the face, but still looks natural. And as of yet, I have not seen any irritant or allergic contact reactions to the makeup. It's claim to fame is that it is almost solely made of finely pulverized natural minerals and does not contain fillers and preservatives. Since the fillers and preservatives are common allergens and irritants, the pure mineral makeup could be safer for sensitive skin. However, there is no regulatory body certifying the purity of this makeup so it is up to the consumer to check ingredients. There are lots of companies out there (as evidenced by a simple Google search), and it is difficult to know which ones are better and safer. As with sunscreens, there is concern over the safety of nanoparticles being applied to the skin as there would likely be increased absorption. The absorption of topical powdered minerals has not been studied, so I cannot comment on this either way. One of these weekends, I'm going to explore the makeup counters at the mall and see what sorts of products are out there and what ingredients they use...

I've been away

I've been away for a couple months doing rotations at other medical schools and have fallen behind on my posts. Many are in the works and I just haven't had time to read all the journal articles before posting. Now that I'm back, look for the daily posts.