Genuine Haarlemmer Oil is sold in drugstores and pharmacies, it is still available in the wellknown dropper bottles, it can be administered 'the old fashioned way': on a lump of sugar. It is also sold in taste-and odour-free capsules.
It is widely used in the equestrian world, in poultry and small livestock industry, and used with pigeon racing.
If applied according to the instructions the medication is safe and produces excellent results without side effects or risk to public health. This has been proven through centuries of use.
Unfortunately in this modern era some sectors have limited its use as a preventive application to animal food. About 40 years ago a poultry farm eliminated the prevailing and potential diseases by using Haarlem Oil, it resulted in never having any health issues with the chickens. Three weeks before slaughter they would stop administering Haarlem Oil, thus eliminating the risk of its potential influence on taste or smell.
Until to their dismay, an umbrella organisation forced them to switch over to large, way more expensive quantities of prescribed antibiotics.
From then onwards it was illegal to continue to use our successful and proven medication. Breeders would risk a penalty of exclusion by the agricultural board if they did so. (The dire conseqences of all current preventive and overuse of antibiotics in humans and animals have now become clear.)
Links: Hendrik Tilly, family member of the inventor of Haarlem Oil, Claes Tilly. Hendrik was born in 1662 and died at an age of 105 in 1767. The regular use of Haarlem Oil can still promote longevity.