The best defense against tear gas is a gas mask, but if you don't have a mask there are still steps you can take to minimize damage from tear gas. If you think you might encounter tear gas you can soak a bandana or paper towel in lemon juice or cider vinegar and store it in a plastic baggie. You can breathe through the acidified cloth for several minutes, which should give you sufficient time to get upwind or reach higher ground. Goggles are a great thing to have. You can use tight-fitting swim goggles if chemical safety goggles aren't available. Don't wear contacts anywhere you might encounter tear gas. If you are wearing contact lenses, immediately remove them. Your contacts are a loss as is anything else you can't wash. You can wear your clothes again after you wash them, but wash them separately that first time. If you don't have goggles or any sort of mask, you can breathe the air inside your shirt, since there is less air circulation and therefore a lower concentration of the gas, but that is counterproductive once the fabric becomes saturated.

First Aid

First aid for eyes is to flush them with sterile saline or water until the stinging starts to abate. Exposed skin should be washed with soap and water. Breathing difficulties are treated by administering oxygen and in some cases using medication that are used to treat asthma. Medicated bandages can be used on burns.