I wholeheartedly recommend Dr Lankester's guide, which should be compulsory reading for every foreigner heading for the Himalaya (and the Indian sub-continent as a whole) - whether young or old.  I owe Ted a considerable debt as he recommended a solution to my serious, long-standing gastro-intestinal vulnerabilities when travelling on my expeditions, such that on several occasions, the problem was resolved within 24 hours!  If only I had been given this on my first ever expedition with the University of Southampton Ladakh Expedition back in 1980, when, instead, all we had was a bottle of 'Kaolin & Morphine', which as soon as I tasted it, caused me to vomit... I was forced to abandon the expedition after several weeks, fortunate to get back home, alone, in one piece.... The leader and co-leader of that trip did not have a clue in terms of basic hygiene or providing a satisfactory medical kit. I strongly advise that anyone travelling off-the-beaten-track in the Himalaya, has had First Aid Training and carries a suitable First Aid and Medical Kit - however, you must consider whether you can trust your travelling companions.  I was taught a valuable lesson - don't trust anyone. Those in charge of my first expedition, which could easily have led to long-term health issues or even my death, were criminally negligent, whilst the first-timers, were woefully ill-prepared.