Being able to quickly and accurately identify the various skin types is crucial for the longevity of any indoor tanning facility. Every tanner should be skin typed and recorded, either in a computer file or card file for easy reference. The tanner also should be asked about any medications he or she may be taking and directed to the list of photosensitizing agents posted in the salon.
Skin typing will help tanners know how many sessions it will take to establish a base tan and how long they can be in the tanning unit without experiencing an uncomfortable and unnecessary sunburn. Remember, skin type determines the amount of natural protection a person has against ultraviolet light.
Because of the variety of people with different genetic backgrounds, dermatologists categorize humans into six different skin types, starting from lightest and working up to darkest. Fair skin burns easily and produces little tan because it has little natural protection. Dark skin tans more easily and burns less because it has more natural protection. Therefore, lighter shades should tan for relatively short time periods, while darker shades may tan for more extended periods of time. However, for liability reasons no one should be allowed to exceed the maximum exposure time posted on the unit, no matter how dark his or her skin tone. This chart outlines the six classes of skin types.
This formula is only one variable in the entire tanning equation. It is a common misconception that because indoor tanning equipment is designed to produce a fast tan without burning, tanning for a longer period of time will generate a faster tan. The reality is that the best tanning performance will be achieved by adhering to the maximum recommended exposure time of the individual tanning unit.
Food and Drug Administration standards require equipment manufacturers to provide an exposure schedule with the product warning label. The exposure schedule allows a user to gradually build a tan and maintain it while controlling the risk of acute injury and delayed adverse effects. Because the UV dose that causes a barely discernible pink coloration on the skin is not the same for everyone, the exposure schedule for the first-time user will depend on his or her skin type.
In addition to preventing burns from overexposure to UV light, the formula marks the point at which tanning takes place most efficiently. After this point, the degree of tanning is lessened or even reversed. Even if the tanner already has a substantial base tan, overexposure mostly produces a thickening of the outer layer of skin, which does not tan. Overexposure in a single session may damage the tanning response so that less pigment is produced instead of more.
Because the output of different tanning lamps varies, so will the exposure times of different tanning units. In particular, reflector and high-pressure tanning lamps will have shorter recommended exposure times. But because they are derived from the levels of UV light that the unit produces, they should be respected.
Minimum Erythemal Dose and Minimum Melanogenic Dose
MED is the minimal erythemal dose and is defined as the threshold dose that may produce sunburn. MMD, on the other hand, is the minimal melanogenic dose and is equal to the lowest dose required to develop a visible suntan. Even though the terms MED and MMD seem to be self-explanatory at first glance, the translation of these values in the daily practice of indoor tanning often leads to misunderstandings or wrong interpretations, especially when it comes to determining exposure times based on MED and MMD values.
Assume that unprotected skin has been exposed to UV radiation for the first time. In order to determine the MED, the reaction of the skin will be recorded 24 hours after exposure. The minimal dose that induces any visible skin reddening at that point of time is defined as 1 MED. Redness that occurs immediately after exposure and disappears during the following three to five hours is caused mainly by heat and is not comparable with real UV erythema. This is the reason why the reading is not taken until 24 hours later.
For users of tanning units, the MED provides important information about the sunburning effect of the equipment, since perceptible reddening is the first sign of a sunburn reaction. In order to prevent possible acute or long-term risks due to indoor tanning, the MED should not be exceeded during a session.
The MMD is determined in a very similar manner. In contrast to the MED examination, the readings are performed seven days after exposure instead of 24 hours. The minimal dose required to produce an even, noticeable tan, which can still be observed seven days later, is defined as 1 MMD. The interval between exposure and reading is necessary to permit the occurrence of new melanin biosynthesis (melanogenesis), which only becomes evident after several days of UV application.
To better understand MED and MMD, it should be said that both are individual values. The lowest effective dose developing a sunburn as well as the value producing a suntan depend distinctly on the skin sensitivity of the person.
In order to eliminate these individual influencing factors, MED and MMD have been standardized. With standardized MED and standardized MMD values, sunlamp products can be characterized and become comparable with respect to their biological capabilities. Such information based on these standard values are of higher ranking meaning than are statements about the physical data such as UVB/UVA ratio or UVB percentage.
Comparing Standard MED and MMD
By comparing MED and MMD values of tanning units, it may be surprising that the required exposure time for reaching 1 MMD is usually longer than the corresponding time for reaching 1 MED. This seems to indicate that it is impossible to tan without first developing skin redness. At the same time, the question comes up: How can we achieve tanning slowly, progressively and safely without producing a sunburn?
MED and MMD are standardized values and valid for unprotected and untanned Skin Type II. This means that such given values are basically only valid before undergoing the first exposure.
The effect on the skin of a melanogenic dosage will become evident only three to five days after exposure, at the earliest. Further, melanogenesis is a long-lasting process, therefore, consecutive single dosages work cumulatively. In other words, the skin does not forget the induced pigment effects; it accumulates these single pigment-producing dosages over time. Besides melanogenesis, there exists the IPD, an immediate pigment darkening effect which is a rather superficially effective tanning mechanism. IPD is a transient reaction induced by the photochemical oxidation of pre-formed melanin pigments by long-wave UV, darkening the skin during exposure.
By use of a tanning unit, for example, which is characterized by an exposure time of 20 minutes for 1 MED and 45 minutes for 1 MMD, melanogenesis can be induced in two different ways.
MED/MMD-Based Schedule
Consider the given MMD exposure time of 45 minutes. Although the applied melanogenic dose is high enough to produce new pigments, an exposure of this duration cannot be recommended because the MED would be exceeded more than twice during such a session. The better way to get a tan will be by starting an exposure schedule consisting of three applications of 15 minutes each during one week. The advantage of such a procedure is twofold. The applied dose per session does not reach the limit of 1 MED; however, at the same time the skin has received a total melanogenic dose of 1 MMD. This means the process of new pigment formation will be induced without the risk of sunburn and the skin will remain healthy. Furthermore, at the beginning of each tanning session series, this exposure schedule is in agreement with FDA regulations.
In addition to melanogenesis, even during the first exposure session the skin will be tanned immediately if the horny layer contains some weakly colored, pre-formed pigments which then can be darkened by IPD. Generally, human skin has some pigment pre-stages available (except Skin Type I). In this context, it may be helpful to know that with most of the commonly used sunlamps, the threshold dose to initiate IPD will be reached quicker than 1 MED.
Depending on the amount of available pigment pre-stages (and on skin types) the effect of IPD usually remains only for hours—at the most a few days. With an increasing number of sessions, the amount of pre-stage pigment will be enhanced.
Talking about indoor tanning as well as outdoor tanning, the mechanisms of immediate pigment darkening and of pigment formation (melanogenesis) interact so that a clear differentiation between both is often impossible. As a rule, it can be established that IPD is more important during the first sessions while melanogenesis comes more and more into play during the following exposures.
By using tanning units, both mechanisms are utilized. At the beginning, the tanning results are caused mainly by IPD. With increasing sessions the obtained suntan becomes darker and deeper due to further melanin synthesis.
Further, with well-tanned skin, the required exposure time to develop an erythema will be prolonged, and provide an effective sun protection.
