Showering less frequently, such as extending the time between showers to two weeks, will not typically cause immediate harm, but it could have some negative effects. Your skin and hair can accumulate oils, sweat, dead skin cells, and bacteria, which might lead to body odor, itchiness, or irritation. Additionally, if you engage in physical activities or live in a hot climate, the effects may be more pronounced.
In general, how your skin and hair respond can depend on your personal hygiene, skin type, and any pre-existing conditions. If you decide to wait two weeks, just be mindful of any changes in how you feel or your skin condition, and make sure to maintain cleanliness in other ways if needed.