Clean your dried leather chair to remove dirt buildup, which can wear and further dry the upholstery. Commercial cleaners tend to have common similar ingredients, including lanolin, olive oil or animal-rendered oils. Store-bought cleaners come in liquid form and wipes. Touch-up kits are also available for scarring and discoloration, although with several treatments over time, they will fade anyhow. If you do purchase a touch-up kit, look for one that matches the chair's color as closely as possible.
Make a cleaner and conditioner to bring your chair back to life. Several applications may be required over time to fully restore the chair. Apply the treatment more frequently if you live in a dry climate. Mix 1 part distilled white wine vinegar with 2 parts linseed oil in a container. Dip a clean, lint-free cloth in the mixture, and apply it to the chair in a swirling pattern. Cover the chair evenly and completely. Let the treatment sit overnight, and buff the entire chair with a clean cloth to bring out the shine.
If you've kept your leather chair fairly clean without treating it with conditioner, it may be extremely dry from being stripped often. Dip a clean cloth in pure linseed oil, and apply it evenly to the chair's surface area. Allow the oil to sit overnight before buffing. Wait a day or two before sitting on the chair as the fresh oil can stain clothing. Vaseline also works well if you don't have linseed oil, and it acts as a water protectant as well, so it's very effective for patio chairs.
Avoid using household cleaners on a leather chair, dry or otherwise. While cleaning leather normally removes a small amount of dye, household cleaners can strip off more color than leather cleaners. Mineral spirits and turpentine also pull color from leather. Stay clear of leather cleaners and treatments containing alcohol as they dry out the leather further. Conditioners with animal fats like milk oil darken the leather color.