Hello my friend,
I can understand your concern and I will do everything I can to help you. Yes you are correct mesquite tree thorns are poisonous to both humans and animals. These desert type plants can cause a reaction but they are not known to cause death or any serious injury. The main problem is that the thorns can cause an infection if not treated properly. The way you treat this type of injury is by pouring hydrogen peroxide on the wound to be sure that any bacteria is killed. Then be sure to saturate the area with an antibiotic cream such as neosporin. Then dress the wound and be sure to keep the area clean. You can use a band aid or dressing. You should be fine and the peroxide should help to clean out any poisons as well. However you need to be aware that if you experience any swelling or pain in that area that you need to go the doctor right away. Stop soaking your foot in epsom salts and this can cause further irritation for this type of injury.
I hope you feel better soon. Please click on accept otherwise please request more information. I am here for you any time.