Since the 1950s, rates of multiple sclerosisplugin-autotooltip__plain plugin-autotooltip_bigMultiple sclerosis

Multiple sclerosis (MS) is a severe persistent condition of the central nervous system in which the coating around nerve fibres (myelin) is damaged, causing a wide range of distressing symptoms varying in severity.

At any given time, it affects around 3 million people worldwide. , Crohn's diseaseplugin-autotooltip__plain plugin-autotooltip_bigCrohn's disease

Crohn's disease is a type of inflammatory bowel disease (IBD) that can affect any part of the entire digestive tract. It causes inflammation and in severe cases, ulcers can form. Symptoms often include abdominal pain, diarrhea, fever, abdominal distension, and weight loss., type 1 diabetesplugin-autotooltip__plain plugin-autotooltip_bigDiabetes (type 1)

Type 1 Diabetes is a chronic autoimmune disease that occurs either when the pancreas does not produce enough insulin, or when the body cannot effectively use the insulin it produces. Insulin is a crucial hormone required for the body to regulate and use blood sugar., and asthmaplugin-autotooltip__plain plugin-autotooltip_bigAsthma

Asthma is a common, (and currently incurable) long term inflammatory disease of the airways of the lungs, characterized by variable and recurring symptoms such as reversible airflow obstruction, and bronchospasm. Episodes of asthma frequently feature wheezing, coughing, chest tightness, and shortness of breath.have soared by 300% or more. Similar graphs depict concurrent spikes in hay fever and food allergies." ^{[our hyperlinks]}

Source : Proc Natl Acad Sci U S A. 114(7): 1433–1436.

This huge increase in auto-immune diseases and allergiesplugin-autotooltip__plain plugin-autotooltip_bigAllergies

The word 'allergy' was coined in 1906, and is used to describe people's immune system hypersensitivity to seemingly harmless substances in their environment.

Allergic reactions can be light - e.g. a mild skin rash - or life-threatening if it leads to has yet to be convincingly explained.

In 1989 “The Hygiene Hypothesis” was proposed - the core idea being that early childhood exposure to micro-organisms and parasites etc. might stimulate the development of a strong immune system.

It has been widely suggested that in 'Westernised' or 'developed' societies, where hygiene is given a relatively high priority, children's immune systems do not develop properly, and instead turn towards attacking the body's own tissues and structure rather than pathogens.

Thirty years or so after its conception, however, the hypothesis is not as enthusiastically embraced as it once was. Various inconsistencies having been pointed out - see the literature cited above.

Also see :'Time to abandon the hygiene hypothesis: new perspectives on allergic disease, the human microbiome, infectious disease prevention and the role of targeted hygiene' Perspect Public Health. 136(4): 213–224.