Where you attend undergrad has no bearing on what medical specialty you eventually end up in. Specialty is all about med school performance and board scores (USMLE). I would strongly suggest you NOT plan on med school if derm is the only medical specialty you want to practice. (Derm is among the most competitive of specialties and even among the very top med students nationally only 70% of those applying for derm match into the field.)
Let me repeat this for emphasis: If you wouldn’t be happy as a family practice doc or general internist—don’t go to med school.
Major is a matter of preference. Med school admissions is about GPA, MCAT scores, ECs and LORs. Med schools accept people from all majors so long as they have completed the prerequisite coursework (bio, gen chem, ochem, biochem, physics, calc, stats, English, soc, psych) Choose a major you enjoy and will do well in.
Every 4 year college in the US offers the necessary coursework to fulfill med school admission requirements. Choose one that fits you and that is affordable.