Red Line Rash on Back of Hand Spreading (Photo)?

That is a contact dermatitis. So, you've touched some item (probably a plant) during your hike. Poison ivy/oak would be the leading candidate. It generally takes 2 to 10 days after exposure to break out, depending upon how allergic you are and the amount of plant oil that got onto your skin. Keep up with the hydrocortisone cream, until your dermatologist can get you a stronger product. Cool, wet cloths also make it feel better, and oral benadryl might take the edge off, too.