Yep, 37.5 is the upper end of normal. Did you use a tympanic thermometer?

The RCH in Melbourne recommends not treating a fever below 39.C. A fever is the body's way of creating an inhospitable environment for bacteria or a virus. By reducing a low grade fever we are actually preventing the function of the body's own defence system.

Keep an eye on your DS, sounds like a day of snuggles might be in order!