When working with pallet wood, be alert to any adverse health symptoms, because the wood dust may be the culprit. Pallets can be a source of unique woods, especially from some of the off-shore places. It would be best to wear respiratory protection, because there is no way of you knowing what insecticides/biocides they have been treated with to meet import/export regulations. Many of the chemicals banned or highly restricted in the US are still used by many countries. Just because it came to you from a US source does not mean that is where the pallet originated.
Yeah, I know. Preaching to the choir! LOL