If this is a Pathfinder 1st Edition question:
I'd say that you do not need a disguise kit specifically to make a disguise, but that if you don't have one there needs to be some explanation of how you're disguising yourself.
Basically, having the kit gives a +2 and means I'll assume you have everything you need. No kit, you're rolling flat and you need to tell me what you're doing. If you don't have the purpose built kit with everything you need, you need to make use of stuff in your area which requires some explanation. I wouldn't demand a super in-depth explanation, just something simple.
Also, flagged for the wrong forum
If this is a Pathfinder Playtest question:
The Impersonate use of the Deception skill specifically states it needs a Disguise Kit, so yeah you need one.