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Sun Exposure and Skin Health
Public health campaigns that advocate total protection from UV rays overlook the crucial role that solar-derived vitamin D3 plays in overall health and in protecting skin from sun damage. Chronic sun exposure is a risk factor for both squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). Although short-term intense UV exposure (sunburn), particularly during childhood, has been linked to malignant melanoma (MM) in epidemiology studies, chronic sun exposure has not. In fact, several studies indicate that chronic exposure that does not produce sunburn may protect against MM, according to Jörg Reichrath and Sandra Reichrath. They suggest that skin-produced D3 "may represent an evolutionary highly conserved feedback mechanism that protects the skin from the hazardous effects of solar UV-radiation." In vitro and in vivostudies support vitamin D's protective effect.
Vitamin D has been primarily associated with bone formation, but it also regulates numerous cellular functions, including cell growth and differentiation. Vitamin D receptors and the main enzyme needed to convert 25(OH)D to biologically active 1,25(OH)2D are found in tissues throughout the body. Without sufficient sun exposure, vitamin D deficiency results. Vitamin D deficiency is associated with increased risk or poor prognosis for several diseases including skin, colon, prostate and breast cancers; autoimmune disease; infectious disease; and cardiovascular disease.
"The important take home message for dermatologists and other clinicians is that health campaigns promoting strict sun protection procedures to prevent skin cancer may increase the severe health risk of vitamin D-deficiency," state the authors.
The Vitamin D Foundation recommends moderate, frequent sun exposure: "Large amounts of vitamin D3 (cholecalciferol) are made in your skin when you expose all of your body to summer sun. This happens very quickly: around half the time it takes for your skin to turn pink and begin to burn." People with very light skin need only 15 minutes of exposure, while those with darker skin may need a few hours to make a good supply of the vitamin. Dark skin contains more melanin that blocks UVB needed for D3 production.
Public health agencies usually advise people to avoid midday summer sun. The Vitamin D Foundation, however, points out that the earth's atmosphere blocks UVB rays early and late in the day and during most of the winter. Exposing as much skin as possible to sun for short periods near midday is the most effective way to increase D3. "A good rule of thumb is if your shadow is longer than you are tall, you're not making much vitamin D," according to the group's website. To avoid overexposure, the Vitamin D Foundation recommends covering up with clothing or staying in the shade. Studies investigating sunscreen's ability to prevent skin cancers have had mixed results.
Reichrath J, Reichrath S. Hope and challenge: the importance of ultraviolet (UV) radiation for cutaneous Vitamin D synthesis and skin cancer. Scand J Clin Lab Invest. 2012;72(Suppl 243):112–119. Available at EBSCO. Accessed April 24, 2015.
How do I get the vitamin D my body needs? [online article]. Vitamin D Foundation. www.vitamindcouncil.org/about-vitamin-d/how-do-i-get-the-vitamin-d-my-body-needs/#. Accessed April 24, 2015.
Tea Tree Oil in Dermatology
Topical application of tea tree oil (TTO), the steam-distilled essential oil derived from the Australian shrub Melaleuca alternifolia, is an effective treatment for many skin disorders. The oil contains terpinen-4-ol, a powerful antimicrobial and anti-inflammatory agent. TTO also has antioxidant and antitumor effects. A 2013 literature review, conducted by Nader Pazyar, MD, and colleagues, discusses in vitro, in vivo,and clinical research that supports TTO's use for dermatologic conditions.
The review is the first to summarize TTO's possible applications for dermatology. TTO has antiviral, antifungal, antiprotozoal, and antibacterial activity, according to the review. A 10% concentration of TTO showed results against S. aureus comparable to topical mupirocin. TTO is an "efficient" treatment for hand warts caused by human papillomavirus. Fungal infections of the nails, athlete's foot, and seborrheic dermatitis improve with topical TTO. A combination of TTO and lavender oil was highly effective for killing head lice, according to a 2010 study by Barker and Altman. In addition to having antimicrobial activity, a topical 10% TTO-dimethyl sulfoxide (DMSO) formula significantly slowed subcutaneous melanoma growth in mice. The authors say, "In conditions for which TTO treatment is of benefit, further research is necessary to establish guidelines for its application, preparations, and therapeutic indices."
Topical application may not be the only method for using TTO. Karen B. Chin, RN, and Barbara Cordell, PhD, RN, reported clinical evidence that exposure to TTO fumes increased healing rate of infected wounds. Their small 2013 study involved 10 patients with abscessed wounds infected with Staphylococcus aureus. Two pairs of participants ("matched as closely as possible by age, gender, infectious vector, and number of days with infected wound") provided a mini-controlled experiment; 1 person in each matched pair received a standard dressing. The other 2 along with the 6 unmatched participants were treated with TTO dressings (changed every three days). The dressings consisted of 6 pipette drops (about 2 drops from a regular dropper) of full-strength TTO centered on the abdominal pad, Telfa pad, or gauze. Some participants also received antibiotics. Nurses recorded the wound size and description when dressings were changed.
Both matched pairs showed a marked difference between the conventional treatment and the use of TTO dressing. In pair A, the control's thigh abscess took over a week to begin healing, but the TTO patient's buttocks abscess showed major improvement after 1 day. In pair B, the control's calf abscess showed little improvement at day 19, whereas the TTO patient's scalp abscess was healing well at day 3. When the woman with the calf abscess (pair B) was given a TTO dressing, she reported that the wound closed after 1 day and was no longer painful. Five of the 6 unmatched participants also recovered quickly (an average of 4.4 days) with TTO treatment. One patient did not respond to TTO: a 70-year-old man with diabetes, hypertension, and respiratory illness.
"Further study is warranted to observe the effects of tea tree oil with and without conventional antimicrobial pharmaceutical treatment for both S. aureus and MRSA," say Chin and Cordell.
Barker SC, Altman PM. A randomized, assessor blind, parallel group comparative efficacy trial of three products for the treatment of head lice in children. BMC Dermatol. 2010;10:6. Available at www.ncbi.nlm.nih.gov/pubmed/20727129. Accessed May 15, 2015.
Chin KB, Cordell B. The effect of tea tree oil (Melaleuca alternifolia) on wound healing using a dressing model. J Altern Comp Med. 2013;19(12):942–945. Available at EBSCO. Accessed April 28, 2015.
Greay SJ, Ireland DJ, Kissick HT, et al. Inhibition of established subcutaneous murine tumor growth with topical Melaleuca alternifolia (tea tree) oil [abstract]. Cancer Chemother Pharmacol. 2010;66:1095-1102. Available at www.ncbi.nlm.nih.gov/pubmed/20577741. Accessed May 15, 2015.
Pazyar N, Yaghoobi R, Bagherani N, Kazerouni A. A review of applications of tea tree oil in dermatology. Int J Dermatol. 2013;52:784–790. Available at EBSCO. Accessed April 28, 2015.
Ticks and Biodiversity
Although Lyme disease first gained attention in the 1970s, the causative spirochete Borrelia burgdorferi (Bb)is no newcomer. "Distinctive Bb genes have been identified in museum collections of ticks from the 1940s and of white-footed mice from the turn of the twentieth century," says science writer Sharon Levy. Decreased biodiversity in the environment may be one reason that Lyme incidence has risen to an estimated 20,000-30,000 cases annually in the US (CDC figures).
Deerticks (Ixodes scapularis) are not born with Bb infection. The larvae, which hatch on the ground, become infected when they feed on blood from small infected animals. White-footed mice are the primary carriers of Bb. Other small animals, such as raccoons and skunks, are less likely to transmit Bb. If a tick larva has the misfortune of hopping onto an opossum for its first meal, it may not survive to see the next (nymph) stage of its life cycle. In 1990, epidemiologist Durland Fish found that 40% of the nymphs that had fed on white-footed mice acquired Bb (the highest infection rate for any tested host animal), but those that fed on an opossum died before researchers could test them for infection. Tiny nymphs need a second blood meal in order to become adults that reproduce. Both nymphs and adult ticks reside on vegetation instead of the ground, so their prospective hosts are larger mammals such as deer and humans.
The increased incidence of Lyme has been linked to at least two changes in biodiversity, according to Miriam Pfäffle, Nina Littwin, and Trevor N. Petney. First, the numbers of white-footed mice and other small mammals have increased because their major predator, the red fox, is less prevalent. Second, deer populations have also expanded with the absence of their primary natural predators. "Although deer are not competent vectors of B. burgdorferi s.s., and seem to have little or no role in the maintenance of infection in ticks, deer are the most important hosts for [adult] female ticks," explain Pfäffle and colleagues. More deer lead to more tick larvae, larvae that are available to become infected.
Levy S. The Lyme disease debate. Environ Health Perspect. April 2013;1221(4):A120–129. Available at http://ehp.niehs.nih.gov/121-a120. Accessed April 24, 2015.
Pfäffle M, Littwin N, Petney TN. The relationship between biodiversity and disease transmission risk. Res Rep Biodivers Studies. 2015;4. Available at www.researchgate.net. Accessed April 24, 2015.
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