allergen – a substance that causes an allergic reaction. Allergens stimulate the body’s immune system to produce antibody proteins, to counteract the allergen. Examples of common allergens include dust, pollen, pet dander and mould.

allergy – an exaggerated immune response to allergens, such as insect venom, dust mites, pollen, pet dander, drugs or some foods.

analgesic – a medication that relieves pain.

autoimmune disease – a disease in which the immune system destroys or attacks the patient’s own body tissue.

autonomic nervous system – the part of the nervous system that regulates key automatic bodily functions, including the activity of the heart muscle and smooth muscles such as the gut.

bioaccumulation – the accumulation of substances from the environment by animals and plants over time. A number of pollutants (see persistent organic pollutants) can be stored for years in human body fat and can be discharged in a woman’s breast milk.

biofeedback – a technique that uses electronic monitoring equipment to train people to control bodily functions which are normally automatic, for example, their blood pressure, heart rate or muscle tension.

body burden – the total amount of toxins that have built up over time in a person’s body.

brain fatigue – also referred to as “brain fog.” This term is sometimes used by patients with chronic fatigue syndrome, fibromyalgia and environmental sensitivities, to describe difficulty concentrating, thinking and remembering, and a dull, groggy or “spacey” feeling.

chronic disease – an illness that lasts for a long time.

chronic fatigue syndrome – a chronic condition characterized by fatigue, post-exertional malaise and/or fatigue; can also cause headaches, sore muscles, joint pain and fever; not directly caused by other conditions. People with chronic fatigue syndrome are not able to fully participate in their ordinary activities.

cognitive – relating to conscious intellectual activity (such as thinking, reasoning, remembering, imagining or learning words).

cognitive behavioural therapy – a form of psychotherapy that emphasizes the importance of finding new ways of thinking and behaving to deal with current problems, such as depression or anxiety.

cumulative toxic effects – the result of a build-up of a toxin or a number of toxins over time in the body, as a person is repeatedly or continuously exposed.

dioxins – highly toxic chemicals which are by-products of incineration or chlorine bleaching. More than 90 percent of human intake of dioxins is from food, especially animal fats, herbicides and pesticides. Acute health effects include headaches and nausea. Cancers, diabetes, liver disease, heart disease, fatigue and nerve and reproductive damage have been reported in humans exposed to high levels.

endocrine disrupters – chemicals that affect the endocrine system and prevent hormones from performing their usual functions in the body. Exposure to endocrine disrupters during critical stages of development can result in permanent effects on overall health, intelligence and the ability to reproduce. Examples of endocrine disrupters include PCBs, some pesticides, dioxins and phthalates.

endocrine system – the system of glands that regulates a person’s mood, growth, sexual function, reproductive processes and metabolic activity. The endocrine system includes the pituitary gland, thyroid, parathyroids, adrenal glands, pancreas, ovaries (in women) and testes (in men).

environmental contaminants – potentially harmful substances that have been released into the environment and have entered our food, water, air and soil.

fibromyalgia – a chronic condition that causes pain and stiffness throughout the tissues that support and move the bones and joints. Pain and localized tender points occur in the muscles, particularly those that support the neck, spine, shoulders and hips. The disorder includes widespread pain, fatigue and sleep disturbances.

flare-up – a period in which the symptoms of a disease reappear or worsen.

heavy metals – dense metals of high relative atomic mass, such as lead, cadmium and mercury. Heavy metals can accumulate in the tissues and are toxic beyond certain levels, which vary from person to person.

hidden exposures – exposures to toxins or environmental contaminants that people are unaware of. Exposures occur by breathing in, eating, drinking, touching or injecting a substance.

immune response – the reaction of the immune system against foreign substances. When this reaction occurs against substances or tissues within the body, it is called an autoimmune reaction.

immune system – a complex system that normally protects the body from infections and environmental contaminants. It is comprised of groups of cells, the chemicals that control them, and the chemicals they release.

inflammation – a reaction of tissues to injury or disease, marked by swelling, redness, heat and pain.

ligaments – bands of cord-like tissue that connect bone to bone.

malaise – a general feeling of unease or lack of health, often accompanying the onset of an illness. Post-exertional malaise follows either physical or mental activity.

musculoskeletal – referring to the muscles, tendons, ligaments, cartilage, bones, joints and spinal discs.

myalgic encephalomyelitis – the British term for chronic fatigue syndrome.

neuroendocrine – relating to the interactions between the nervous and endocrine systems.

neurologic – referring to the brain and central nervous system. The “central” nervous system is comprised of the brain and spinal cord. The “peripheral” nervous system is the nerve tissue that transmits sensation and motor information back and forth between the body and the central nervous system.

nonsteroidal anti-inflammatory drugs (NSAIDs) – a group of drugs, such as aspirin and ibuprofen, used to reduce inflammation.

off-gas or off-gassing  – to give off fumes. Substances such as solvents, paints, certain cleaning products, plastic materials (e.g., shower curtains) and pesticides “off-gas.”

PCBs (polychlorinated biphenyls) – a class of highly toxic synthetic chemicals that were used from 1929 to 1979 in North America, in industrial materials, and in transformers and other electrical equipment. The manufacture and importing of PCBs were banned in 1979, in North America, due to their environmental persistence, bioaccumulation in fatty tissues and potential health risks. They are still found in foods and the environment (water systems, landfills and hazardous waste sites). PCBs can be toxic to the liver and skin, and can cause cancer.

persistent organic pollutants – pollutants that remain in the environment for a long period of time, are stored in fat, and are toxic. Examples of POPs include dioxins, PCBs, lead, arsenic, cadmium, mercury and chlorinated pesticides.

precautionary principle – a moral principle used to guide decisionmaking and prevent harm: When there is an activity or product that could threaten human health or the environment, precaution should be taken, even before there is scientific proof that the activity or product is harmful. The precautionary principle advises caution in the context of uncertainty. It is often applied, for example, in the realms of environmental policy and health care.

RAST test – the RAST (radioallergosorbent test) is an allergy test done with a blood sample. It tests for the amount of specific antibodies in the blood to specific substances.

remission – a period during which the symptoms of a disease are reduced (partial remission) or disappear (complete remission).

restless leg syndrome – a sleep disorder characterized by numbness, tingling, restlessness and a creeping feeling in the legs. Restless leg syndrome is relieved by stretching or walking.

skin or scratch or prick test – an allergy skin test used to identify the substances that are provoking an allergic reaction. It is performed by applying an extract of an allergen to the skin, scratching or pricking the skin to allow exposure, and then evaluating the skin’s reaction.

sleep disorders – a broad range of difficulties related to sleeping. A person may have difficulty falling asleep (insomnia), difficulty staying asleep, difficulty staying awake (narcolepsy) or other disruptive sleep patterns. Sleep disorders have many causes, such as stress, physical illness, abnormalities of the biological clock, drugs and medications, and sleep disturbances that contribute to difficulty achieving restful, restorative sleep.

synergistic effects – effects of a combination of two or more substances that are greater than the sum of the effects of the individual substances. Very little is known about the synergistic effects of our exposures to common chemicals.

toxin – a poison produced by a living organism, such as a plant, animal or micro-organism.

volatile organic compounds (VOCs) – gasses emitted from certain solids and liquids, which can have adverse short- and long-term effects on human health. The thousands of chemicals that are considered VOCs are emitted from products such as paints, paint strippers, varnishes, glues, pesticides, furnishings, building materials, carpet, plastics, gasoline, cigarettes, air fresheners, dry-cleaned clothing, and office equipment, such as photocopiers and printers. VOC levels are generally several times higher indoors than outdoors.