The Minor test is used to visualize increased sweating on the human body. In the process, a specially mixed iodine solution is brushed evenly onto the skin. This is usually a mixture of iodine or potassium iodide, glycerine or castor oil, and alcohol. Once the solution has dried, it is powdered over with a starch powder or quinizarin. The next step is to induce profuse sweating by administering aspirin or lime blossom tea. Areas of the body with particularly heavy perspiration then turn blue to black. Small dots appear on a white background, which increase in size over time and merge (confluence). The method is used especially when patients suffer from increased sweat gland activity in the armpit area. The discoloration is then particularly noticeable there. The minor test often also indicates increased transpiration on the hands. The iodine-starch test was introduced in 1928 and named Minor after its first user.
What is the Minor test?
The chemical mixture used is also called Lugol’s solution. It was invented as early as 1835 by the French physician Jean Guillaume Lugol. Its Latin name is Solutio Lugoli. In its original form, it is a solution of iodine in water to which potassium iodide has been added. Lugoli’s solution is used for extremely diverse purposes in chemistry and medicine, including the detection of chitin or alkaloids and as a disinfectant. It is brownish-red in color and has the typical iodine odor. The classic mixing ratio is 1:2 iodine to potassium iodide in water. The color reaction in the minor test on the skin is based on the incorporation of iodine ions into starch molecules. The Achenbach method is known as a modification of the minor test, in which starch-containing paper impregnated with iodine crystals is used. If this paper is placed on strongly sweating skin areas, it discolors accordingly. This modified test is repeated at certain time intervals to indicate an improvement in the situation. If this occurs, the blue to black discolored area becomes smaller over time. The minor test is still the leading method for verifying hyperhidrosis, the excessive production of sweat. It can occur locally, especially under the arms, on the hands and feet, but can also affect the entire body including the face. When performing the Minor test, it is crucial to thoroughly dry the excessively sweating skin area before applying Lugol’s solution. This is the only way to accurately visualize the affected areas of the body. In addition, gravimetry can be used to precisely determine the amount of sweat secreted in a given time. Here, a special filter paper is used to absorb the sweat. It is then weighed with an ultra-fine balance. However, no limits are set for the result, which could have significance for a possible treatment.
Function, effect and goals
Hyperhidrosis is estimated to affect one to two percent of the entire population in Germany. This condition generally occurs regardless of the temperature and the time of day or year. The vigorous perspiration cannot be consciously controlled without aids. Heavy sweating occurs 60 percent on the hands and feet, 40 percent in the armpits and 10 percent on the head or forehead. For those affected, excessive sweating is always determined by subjective assessment and personal suffering. In science, hyperhidrosis is understood as the production of a total of 100 milligrams of sweat in an armpit in a period of five minutes. Such values aside: Sweating is vital for the human organism because it contributes to the regulation of body temperature. Not only the skin is cooled, but equally the interior of the body, including all organs.
Risks, side effects and dangers
Excessive sweat production can be congenital and in this case is called primary hyperhidrosis. This usually becomes noticeable in childhood to adolescence, occurs unpredictably and cannot be controlled. Secondary hyperhidrosis, on the other hand, is always the result of a disease, usually of the circulatory system.In the case of so-called bromhidrosis, the excess sweat moistens the horny layer of the skin and thus contributes to the proliferation of germ flora, which causes an unmistakable malodor. In relation to the armpits, the minor test can provide valuable information about the extent of hyperhidrosis. It is classified as severe if the sweating areas under the arms are larger than 20 centimeters, as well as sweat dripping from the palms and feet. In addition, generalized hyperhidrosis occurs, for example, during great physical exertion or in the course of the so-called fever. In both cases, sweating here is a regulation of body temperature, which has increased beyond normal levels. The increased sweat production thus releases excessive heat into the environment. However, the Minor test does not provide any information about the reasons for the repeated heavy sweating. For example, hyperhidrosis can have hormonal causes. These may have to do with menopause, hyperthyroidism or, in rarer cases, tumors that emit adrenaline. Circulatory weaknesses and, even more frequently, obesity are also natural causes of persistent increased perspiration. Often this is still strengthened by psychological problems or disturbances as well as particularly straining stress cases.
