Human skin in the context of "Sunscreen"

Medical diagnosis (abbreviated Dx, D_x, or D_s) is the process of determining which disease or condition explains a person's symptoms and signs. It is most often referred to as a diagnosis with the medical context being implicit. The information required for a diagnosis is typically collected from a history and physical examination of the person seeking medical care. Often, one or more diagnostic procedures, such as medical tests, are also done during the process. Sometimes the posthumous diagnosis is considered a kind of medical diagnosis.

Diagnosis is often challenging because many signs and symptoms are nonspecific. For example, redness of the skin (erythema), by itself, is a sign of many disorders and thus does not tell the healthcare professional what is wrong. Thus differential diagnosis, in which several possible explanations are compared and contrasted, must be performed. This involves the correlation of various pieces of information followed by the recognition and differentiation of patterns. Occasionally the process is made easy by a sign or symptom (or a group of several) that is pathognomonic.

Jaundice, also known as icterus, is a yellowish or, less frequently, greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults typically indicates the presence of underlying diseases involving abnormal heme metabolism, liver dysfunction, or biliary-tract obstruction. The prevalence of jaundice in adults is rare, while jaundice in babies is common, with an estimated 80% affected during their first week of life. The most commonly associated symptoms of jaundice are itchiness, pale feces, and dark urine.

Normal levels of bilirubin in blood are below 1.0 mg/dl (17 μmol/L), while levels over 2–3 mg/dl (34–51 μmol/L) typically result in jaundice. High blood bilirubin is divided into two types: unconjugated and conjugated bilirubin.

Skin care or skincare is the practice of maintaining and improving the health and appearance of the skin. It includes washing, moisturizing, protecting from the sun, and treating skin problems like acne and dryness. Skin care can help prevent infections and irritation and is an important part of daily hygiene.

Skin care is at the interface of cosmetics and dermatology. Skin care differs from dermatology by its inclusion of non-physician professionals, such as estheticians and nursing staff. Skin care includes modifications of individual behavior and of environmental and working conditions. Skin care is an essential part of wound healing, radiation therapy, and the management of some medications.

An occupational injury is bodily damage resulting from working. The most common organs involved are the spine, hands, the head, lungs, eyes, skeleton, and skin. Occupational injuries can result from exposure to occupational hazards (physical, chemical, biological, or psychosocial), such as temperature, noise, insect or animal bites, blood-borne pathogens, aerosols, hazardous chemicals, radiation, and occupational burnout.

While many prevention methods are set in place, injuries may still occur due to poor ergonomics, manual handling of heavy loads, misuse or failure of equipment, exposure to general hazards, and inadequate safety training.

Penetrating trauma is an open wound injury that occurs when an object pierces the skin and enters a tissue of the body, creating a deep but relatively narrow entry wound. In contrast, a blunt or non-penetrating trauma may have some deep damage, but the overlying skin is not necessarily broken and the wound is still closed to the outside environment. The penetrating object may remain in the tissues, come back out the path it entered, or pass through the full thickness of the tissues and exit from another area.

A penetrating injury in which an object enters the body or a structure and passes all the way through an exit wound is called a perforating trauma, while the term penetrating trauma implies that the object does not perforate wholly through. In gunshot wounds, perforating trauma is associated with an entrance wound and an often larger exit wound.

Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles in a male. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Before puberty, the external sex organs, known as primary sexual characteristics, are sex characteristics that distinguish males and females. Puberty leads to sexual dimorphism through the development of the secondary sex characteristics, which further distinguish the sexes.

On average, females begin puberty at age 10½ and complete puberty at ages 15–17; males begin at ages 11½–12 and complete puberty at ages 16–17. The major landmark of puberty for females is menarche, the onset of menstruation, which occurs on average around age 12½. For males, first ejaculation, spermarche, occurs on average at age 13. In the 21st century, the average age at which children, especially females, reach specific markers of puberty is lower compared to the 19th century, when it was 15 for females and 17 for males (with age at first periods for females and voice-breaks for males being used as examples). This can be due to any number of factors, including improved nutrition resulting in rapid body growth, increased weight and fat deposition, or exposure to endocrine disruptors such as xenoestrogens, which can at times be due to food consumption or other environmental factors. However, more modern archeological research suggests that the rate of puberty as it occurs now is comparable to other time periods. Growth spurts began at around 10–12, but markers of later stages of puberty such as menarche had delays that correlated with severe environmental conditions such as poverty, poor nutrition, and air pollution. Puberty that starts earlier than usual is known as precocious puberty, and puberty which starts later than usual is known as delayed puberty.

Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is largely the result of genetics (inherited from one's biological parents), and in adults in particular, due to exposure to the sun, disorders, or some combination thereof. Differences across populations evolved through natural selection and sexual selection, because of social norms and differences in environment, as well as regulation of the biochemical effects of ultraviolet radiation penetrating the skin.

Human skin color is influenced greatly by the amount of the pigment melanin present. Melanin is produced within the skin in cells called melanocytes; it is the main determinant of the skin color of darker-skin humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as a consequence of physical exercise, sexual arousal, or the stimulation of the nervous system (e.g. due to anger or embarrassment), arterioles dilate. Color is not entirely uniform across an individual's skin; for example, the skin of the palm and the soles of the feet is lighter than most other skin; this is more noticeable in darker-skinned people.

Body painting is a form of body art where artwork is painted directly onto the human skin. Unlike tattoos and other forms of body art, body painting is temporary, lasting several hours or sometimes up to a few weeks (in the case of mehndi or "henna tattoos" about two weeks). Body painting that is limited to the face is known as face painting. Body painting is also referred to as (a form of) "temporary tattoo". Large scale or full-body painting is more commonly referred to as body painting, while smaller or more detailed work can sometimes be referred to as temporary tattoos.