Allergen — A substance (such as pollen) that induces allergy

Allergy — Abnormal physical reaction to a substance (such as sneezing, breathing difficulty, itching, or skin rashes)

Antibacterial — Destroying or inhibiting the growth of bacteria

Antigen — A substance that is foreign to the body and that evokes an immune response by the body

Antimicrobial — Destroying or inhibiting the growth of microorganisms

Antiseptic — Preventing or arresting the growth of microorganisms

Bacterium (singular) / Bacteria (plural) — a single-celled microorganism that lives in soil, water, organic matter, or the bodies of plants and animals; some cause disease or infection

Contaminate — Corrupt or infect through contact or association

Cross Contamination — The spread of germs from one food (e.g., raw chicken) to another (e.g., lettuce), usually when people don't wash their hands or kitchen utensils after touching the contaminated food.

Disease — Sickness; the impairment of an animal or plant’s normal functioning, manifested by distinguishing symptoms; caused by bacterial infection, mycotic infection, or viral infection

Disinfect — Destroy harmful microorganisms; cleanse

Fungus (singular) / Fungi (plural) — A saprophytic and parasitic spore-producing organism; includes molds, rusts, mildews, smuts, mushrooms, and yeasts; causes mycotic disease

Germ — A microorganism or microbe that causes disease

Germicide — An agent that destroys germs

Hygiene — Practices that are conducive to maintaining health (such as cleanliness); the elimination of microorganisms to prevent infection

Immune — Having a high degree of resistance to a particular disease

Infect — Contaminate with a disease-causing substance (such as bacteria)

Infection — A diseased state caused by the establishment of an infective substance; the establishment of a pathogen in its host after invasion

Microbe — A microscopic or ultramicroscopic organism (as a bacterium or protozoan)

Microorganism — A microscopic or ultramicroscopic organism or microbe (as a bacterium or protozoan)

Microscope — An optical instrument consisting of a lens or combination of lenses for making enlarged images of minute objects

Microscopic — Invisible or indistinguishable without the use of a microscope

Mildew — A usually whitish growth on the surface of organic matter or living plants, produced by fungi

Mold — An usually woolly growth on the surface of damp or decaying organic matter or on living organisms; produced by fungi

Mycosis — Infection with or disease caused by a fungus

Organism — A living being

Parasite — An organism lives in, with, or on another organism as a dependent, without making a useful or adequate return

Pathogen — A disease-causing organism (such as a bacterium or virus)

Pathology —Something abnormal; structural and functional deviations from the normal that constitute disease or characterize a particular disease

Protist — Any of a diverse taxonomic group of unicellular organisms that typically include protozoans, algae, and fungi (as slime molds)

Protozoan (singular) / Protozoa (plural) — A single-cell microorganism, often a pathogenic parasite, that is ubiquitous in soil and water

Sanitary — Of or relating to cleanliness and health

Sanitize — Make sanitary (as by cleaning or sterilizing)

Saprophyte — An organism that obtains food by absorbing organic material that has been dissolved through decay

Spore — A primitive, usually single-celled, often environmentally resistant dormant or reproductive body produced by plants, fungi, and some microorganisms and capable of development into a new individual either directly or after fusion with another spore

Sterile — Free from organisms and especially microorganisms

Submicroscopic — Too small to be seen in an ordinary light microscope

Virus — A submicroscopic agent that can grow and multiply only in living cells and that causes various diseases in humans, animals, and plants

Yeast — A unicellular fungus that reproduces by budding and promotes fermentation; used especially for making alcohol and leavening baked goods