I have acute plantar fasciitis. why would applying ice to the area make it hurt worse? the pain is very sharp. would heat be better?

Ice should not : Make it worse. There is no contraindications to using heat.

Ice is good: Ice massage the area for 5 minutes. Styrofoam cup, fill with water, tear off top 1/4 inch and rub your heel for 5 minutes. See a podiatrist and get evaulated. Heel pain is not a pain that goes away easily. You may need more treatment such as orthotics, anti-inflammatory medicine or a steroid shot are some of the treatment options.

You Can certainly : Try either the ice or heat both can be used. The idea of the ice is if there is inflammation (which is debatable) it will be reduced, the heat can vasodilate the region and bring an influx of blood to possibly heal damaged tissue. My personal recommendation is for ice in the form of a frozen water bottle as this also acts to stretch and massage the plantar fascia.

Combo treatment. : If you have plantar fasciitis, and hurt most with the first few steps in the morning, the more you can do together, the better: #1: supportive shoes. #2: firm inserts or orthotics. #3: oral antiinflammatories (check with your doctor). #4: stretching your foot and calf. #5: icing (10 min at a time). You may also need physical therapy or cortisone injections, or eswt if available in your area.