Natural flea product?

Dear Dr. Marie:

We use Sentry Natural Defense squeeze-on flea control product on our dog, at the correct dosage for his weight. He is only given the treatment every 6 to 8 weeks.

Immediately after treatment we notice he becomes anxious, runs/paces outside, and rolls around on the grass as if to remove the product. This large change in behavior lasts for about 30 minutes, then he's just a bit more antsy than usual after that for between 1-2 hours.

The product is mainly botanical oils (clove, cinnamon, peppermint) and has a strong spicy smell, in a base of isopropyl myristate. I do not see any skin irritation (dryness, redness, etc) at any time after application, nor does his anxiousness include an attempt to scratch at the treated area.

My question is whether his behavior might be a reaction to the strong smell, or could it be burning/irritating the skin regardless of the lack of visual symptoms on the epidermis?

We do not wish to change to a "traditional" chemical form of flea treatment, but would welcome suggestions of other natural topical applications to try. Thank you very much for your consideration.

Related Article: How to get rid of fleas!