HEEELPP!!! My kitten has allergies or a cold??!!! help!! pleease!?

I got my siamese kitten from a shelter a little over a week ago. When we got her, she was the most spunky and playful kitten ever! She wasn't sneezing until yesterday. I just found out that her eyes are getting a little watery. And i think she has more of a little kitty cold than having allergies. What do you think? Do I need to take her to the vet for medicine or will it go away? Please help!