My daughter is 15 months old and 24 pounds. She has a runny nose and allergies. Is there anything I can give her to help?

Runny nose toddler. The only treatments recommended for children under 5 years of age are nasal saline to dry up mucous and decongestant the mucous membranes, and/or a suction bulb to such out excessive or very thick mucous. A cool mist humidified might have some benefit in the bedroom. If the baby is uncomfortable, then tylenol (acetaminophen) or children's Ibuprofen may help.
Allergies. I would talk to your doctor about your childs allergies, many allergy medications are available for 6mo of age and older. Claritin (loratadine) and zyrtec are examples.