Should I take my child to the doctor my 3 yr old daughter has been having diarhhea since yesterday evening. She told me she drank some hand soap yesterday while brushing her teeth.

Anytime . Anytime your child eats or drinks something she shouldn't have, you can call the poison control center toll-free for advice. 1-800-222-1222 this is the number even er doctors and pediatricians use for the most up-to-date advice and treatments for ingestions. If your child is having trouble breathing or is in severe distress after eating something she shouldn't have, this would be a reason to call 911 and go to the er instead. Most likely the hand soap won't hurt her, but it's better to be safe than sorry and worth a call to the poison control center. Legal disclaimer: I am providing this general and basic information as a public service and my response to this question does not constitute a doctor-patient relationship. For any additional information, advice, or specific concerns, please speak with your own physician. The information provided is current as of the date of the answer entry.
Perhaps. Please call your physician to discuss the situation and to ask for advice and/or appointment. There may be other causes for her diarrhea in addition to "drinking soap". In the meantime, keep her hydrated.
Call pediatrician. Call your child's pediatrician who will want to know the brand/type of soap as well as the amount that your child drank. If you cannot reach this doctor, then contact your local hospital emergency room. Or call poison control center.