What should be the molarity of HCl and H2SO4 acid so that they can be considered safe to touch?
According to the Globally Harmonised System (GHS), hydrochloric acid with a concentration of c ≥ 25 % and sulfuric acid with a concentration of c ≥ 15 % are labelled "causes severe skin burns and eye damage" (H314) and are classified based on standard animal test data in skin corrosion Sub-category 1B ("Corrosive responses in at least one animal following exposure > 3 min and ≤ 1 h and observations ≤ 14 days"). "Skin corrosion refers to the production of irreversible damage to skin; namely, visible necrosis through the epidermis and into the dermis occuring after exposure to a substance or mixture."

Hydrochloric acid with a concentration of 10 % ≤ c &lt; 25 % and sulfuric acid with a concentration of 5 % ≤ c &lt; 15 % are labelled "causes skin irritation" (H315) and are classified based on standard animal test data in skin irritation Category 2. "A substance is irritant to skin when it produces rversible damage to the skin following its application for up to 4 hours."

Concentrations well below these values may be considered safe for the exposure of skin to the substance.

Note that the natural skin surface pH is below 5.