Soaking a washable shirt in hot water and either hair conditioner or baby shampoo can help unshrink it. It is important to review care instructions before attempting the process.
One method of unshrinking a shirt is to add hair conditioner to hot water. The shirt can be soaked in the solution for five to 10 minutes. It can be stretched back to a more typical size while still wet and hung to dry.
A similar method uses a combination of water and baby shampoo. Once the shirt has soaked in the mixture it should be wrung out carefully and placed on a towel to dry. As it dries, the shirt can be stretched to its typical size.