. 2020 May 1;2020(5):CD011368. doi: 10.1002/14651858.CD011368.pub2

1. Glossary of medical terms.

Medical term	Explanation
Acne vulgaris	A common chronic skin disorder of sebaceous follicles, mainly affecting the face, chest, and back^a
Chemokine	A group of small cytokines that act as chemical messengers to induce chemotaxis in leukocytes^c
Comedone	A clogged hair follicle in the skin. It can present as a blackhead or whitehead^a
Cytokine	A small protein released by cells that function as molecular messengers between cells^c
Erythema	Redness of the skin, caused by vascular congestion or increased perfusion^b
Hyperkeratosis	Thickening of the outer layer of skin often associated with a quantitative abnormality of keratin^b
Keratinocytes	The predominant cell type in the epidermis, forming a touch protective layer^a
Microcomedones	Early and small plugging of the follicle with excess keratin and sebum^b
Nodule	A solid mass in the skin, more than 0.5 cm in diameter^b
Papule	A circumscribed palpable elevation, less than 0.5 cm in diameter^b
Pilosebaceous unit	A structure consisting of a hair follicle, sebaceous gland, and an arrector pili muscle^b
Propionibacterium acnes (Cutibacterium acnes)	Gram‐positive bacterium related to acne development^b
Pustule	A visible accumulation of free pus^b
Scar	Skin areas of fibrous tissue replacing normal skin after injury^b
Sebum	The oily, waxy substance produced by sebaceous glands^b
Stratum corneum	The outermost layer of the epidermis, where cells have lost nuclei and cytoplasmic organelles^b
Toll‐like receptor	A class of proteins that recognise conserved products unique to microbial metabolism in immune response^c

^aAndrews' Diseases of the Skin: Clinical Dermatology, 11th Edition, 2011, Elsevier Inc. ^bRook's Textbook of Dermatology, Eighth Edition, 2010, Blackwell Publishing Ltd. ^cImmunology, Sixth Edition, 2001, Harcourt Asia Pte Ltd.