How long do headaches last?

I'm wondering if the headache I had last night was related to the Iodine painting i've been doing? What are other negative symptoms people get and how long does it usually last? I'm going on vacation in a week and I don't want to be inducing bigger problems. Could I just be painting on too large an area? I'm painting on the entire front of my neck, and also inside my arm in front of the elbow.

Also, does Iodine cause detox? Why would it do that? I don't see the connection between Iodine and detoxing.

Thanks all!