Interestingly, this is what is on Breitling's own web site:
Like all leather objects (shoes, gloves, etc) a leather strap needs to be carefully cared for in order to maintain its beauty in the long term. Protect leather straps from water, perspiration, damp, grease, perfume, cosmetics or chemicals, and avoid excessive exposure to the sun. The use of Breitling’s care kit (available from brand retailers) will help increase the lifespan of leather straps and maintain their appearance and their supple feel .
http://www.breitling.com/en/service/ind ... ndex=87351