I have seborrheic dermatitis, and i hang out with people who smoke...can the smoke make it worse or interact with the foaming cleansing gel i use?

No, but...: Seborrheic dermatitis patients (including myself) are fortunate in the huge variety of different simple treatments that actually work. Nothing cures it, but it's usually easy to keep under control. If your "foaming cleansing gel" (seborrhea isn't about being dirty) isn't working, there's sulfur, coal tar, ketoconazole, selenium, salicylic acid, "blue shampoo", and much more. Ask.