The state of a compound, solid, liquid, or gaseous is a property which is unrelated to the property / strength of a Brønsted or Lewis acid of said compound. Thus, you can not infer from its physical appearance if an acid is safe enough to be touched by skin; it may be irritant / corrosive even in absence of water (e.g., p-TsOH as a solid acid, triflic acid as a liquid acid). Similar, solid Brønsted bases like KOH or KOtBu are not magically safe to touch once obtained as a solid instead of in solution. The interaction of these acids and bases with the skin may be influenced by water. Your skin however includes many other chemicals which may interact and equally react as an acid, or a base, thus react with external acids and bases accordingly in absence of water, too.
In addition, there are plenty of chemicals (gaseous, or liquid, or solid) which neither are considered as an acid, nor as a base; still, for other reasons than those above these are not harmless enough to be touched over extended periods of time by human skin. Their origin, natural, biological, processed, or entirely artificial, is not a sufficient criterion to render them safe, or potentially dangerous, either. Equally note, skin is not uniform.