A hickey, hickie or love bite in British English, is a bruise or bruise-like mark caused by the kissing or sucking of the skin, usually on the neck or arm. While biting might be part of giving a hickey, sucking is sufficient to burst small superficial blood vessels under the skin.

The origin of the word is from its earlier meaning of "pimple, skin lesion" (c. 1915); perhaps a sense extension and spelling variation from the earlier word meaning "small gadget, device; any unspecified object" which has a unknown origin (1909).

Hickeys typically last from 5 to 12 days and may be treated in the same way as other bruises. Ways to reduce the appearance of hickeys include icing recent hickeys to reduce swelling, rubbing them with a chilled spoon to remove the bruise, and applying a warm compress to older hickeys to dilate vessels and promote blood flow. They can be covered with a concealer or powder corresponding to the sufferer's skin tone, or a fake tan. Alternatively, articles of clothing such as scarves, snoods, turtle necks, or sleeves may be used to conceal hickeys.

Treatment for fiddler’s neck is unnecessary if it is painless and shows minimal swelling, particularly since minor cases are taken as a mark of pride. But fiddler’s neck may lead to worse disorders. The primary methods of treatment involve adjustments to playing of the instrument:

- good hygiene for the affected area and for the instrument

- use of a clean cotton cloth that is changed frequently

- use of a shoulder rest to reduce pressure below the jaw

- a suitable chin rest, especially one carved or molded for the individual

- Covering or changing potentially allergenic materials on the instrument.

- shifting the chin rest to the center of the body over the tailpiece

- smoothing coarse surfaces to reduce abrasion

- for males, growing a beard to avoid folliculitis

Surgery is necessary for sialolithiasis, parotid tumors, and cysts. Cervical lymph nodes that are larger than 1 cm must be biopsied. Connective tissue can be removed by excision when a non-inflamed mass is large, and there is generally little recurrence. Infections should be treated conservatively, and causative species should be identified through smear and culture for appropriate antibiotic selection. Reduction of playing time may be helpful for cases without inflammation, but in 30% of cases this did not improve the symptoms.

Fiddler's neck, sometimes referred to as a "violin hickey," or a "viola love bite" is an occupational disease that affects violin and viola players.

It is a cutaneous condition usually characterized by redness, thickening, and inflammation on the left side of the neck below the angle of the jaw where the instrument is held. Acne-like lesions and cysts may form at the site due to foreign body reactions, and infections may also occur due to poor hygiene. The primary causes of fiddler's neck are constant friction and local pressure. It is well known among professional orchestra musicians but is "not well recognized by dermatologists", and a red mark on the left side of the neck under the jaw "functions as an identifying sign" of a violinist or violist "in public without seeing the instrument""."

Although the presence of fiddler's neck is sometimes used as an indicator of a violinist's skill, or 'battle scars' from constant practice, many violinists never develop fiddler's neck, due to differences in skin sensitivity, playing habits, and the materials used in the construction of the instrument. An accomplished professional player could practice hard their whole life and never develop fiddler's neck.

Microglia are a type of neuroglia (glial cell) located throughout the brain and spinal cord. Microglia account for 10–15% of all cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune defence in the central nervous system (CNS). Microglia (and other neuroglia including astrocytes) are distributed in large non-overlapping regions throughout the CNS. Microglia are key cells in overall brain maintenance—they are constantly scavenging the CNS for plaques, damaged or unnecessary neurons and synapses, and infectious agents. Since these processes must be efficient to prevent potentially fatal damage, microglia are extremely sensitive to even small pathological changes in the CNS. This sensitivity is achieved in part by the presence of unique potassium channels that respond to even small changes in extracellular potassium.

The brain and spinal cord, which make up the CNS, are not usually accessed directly by pathogenic factors in the body's circulation due to a series of endothelial cells known as the blood–brain barrier, or BBB. The BBB prevents most infections from reaching the vulnerable nervous tissue. In the case where infectious agents are directly introduced to the brain or cross the blood–brain barrier, microglial cells must react quickly to decrease inflammation and destroy the infectious agents before they damage the sensitive neural tissue. Due to the unavailability of antibodies from the rest of the body (few antibodies are small enough to cross the blood–brain barrier), microglia must be able to recognize foreign bodies, swallow them, and act as antigen-presenting cells activating T-cells.

Microglia are the primary immune cells of the Central Nervous System, similar to peripheral macrophages. They respond to pathogens and injury by changing morphology and migrating to the site of infection/injury, where they destroy pathogens and remove damaged cells. As part of their response they secrete cytokines, chemokines, prostaglandins, and reactive oxygen species, which help to direct the immune response. Additionally, they are instrumental in the resolution of the inflammatory response, through the production of anti-inflammatory cytokines. Microglia have also been extensively studied for their harmful roles in neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Multiple sclerosis, as well as cardiac diseases, glaucoma, and viral and bacterial infections.