A Letter to a Friend

A Letter to a Friend (written 1656; published posthumously in 1690), by Sir Thomas Browne, the 17th century philosopher and physician, is a medical treatise of case-histories and witty speculations upon the human condition.

Morgellons
It is believed to be the source of a term Mary Leitao found in 2001 to describe her son's skin condition. She chose the name "Morgellons disease" from a skin condition described by Browne in Letter to a Friend, thus:

"Hairs which have most amused me have not been in the Face or Head, but on the Back, and not in Men but Children, as I long ago observed in that endemial Distemper33 of little Children in Languedock, called the Morgellons, wherein they critically break out with harsh Hairs on their Backs, which takes off the Unquiet Symptomes of the Disease, and delivers them from Coughs and Convulsions34."

There is, however, no suggestion that the symptoms described by Browne are linked to the alleged modern cases of Morgellons.

In 1935, Charles Ernest Kellett MD FRCP (1903–1978), who lectured in the history of medicine at the University of Newcastle medical school, wrote a detailed criticism of Browne's Morgellons reference.