Advice from people who travel and work in crowded places:

Expect and be prepared for digestive issues brought on by stress, irregular schedules, and strange food/water:

Imodium, generic - Loperamide, to control diarrhea.

Pepto tablets - generic bismuth tablets, to smooth out digestive problems.

Tums, generic calcium carbonate antacid tablets, to sooth sour stomach from stress or strange food/water.

A supply of bland and known safe food can keep you going if your stomach isn't cooperating. A short supply of Mainstay or other 'survival rations' are usually acceptable. Pick one you like but avoid things you like too much, and things with a lot of flavor. A friend in another country spent three very exhausting days because all they could find that was safe and would stay down was roll of Lifesavers. A box of graham crackers would have been welcome.

Diarhea is a possible outcome of a new location and a sore bung problematic. Baby wipes with aloe, a small tube of Preparation-H, and/or Diaper creme with zinc oxide and balsam can keep things comfortable. These also have use as lubricants, hand creme and to coat minor scrapes.

Your going to be around a lot of people who will be moving around while you try to rest. Invest in ear plugs, the foam ones are usually best. They can be reused by a person a few times if still clean. Also get a sleep mask. Bring spares of both for friends.

Lay in a supply of Benadryl, generic - diphenhydramine, they are safe and effective sleeping pills and a very effective antihistamine. Haiti is a tropical island with a wide variety of potential allergens. Sleep and avoiding allergy attacks are both good.

Haiti is very near the equator. The sun, even in the winter, can flay the skin off your average lily-skinned Yankee in a few hours. A supply, and reserve, of a strong water-resistant sunscreen is going to serve you well. Wide-brimmed hat, long-sleeved shirt, and sunglasses with retainer(and a spare pair) will save you trouble.

With the cool wind coming off the water a fleece jacket is going to feel good after you acclimate to the heat. It also gets cool in the hills.

A short personal supply of Aspirin or whatever headache pills work for you wouldn't be out of place.

Bring your own reserve of toilet paper.

With a lack of clean water, crowds and dead bodies I would bring a supply of mentholated rub to apply under the nose to help with the smell. Haiti is pretty fragrant to start with. Disaster is unlikely to have improved it much.

You can't go wrong with a half-dozen bandannas. Plenty of uses.