Hydrogen Peroxide solutions are typically stored in dark brown opaque containers. Why?

Hydrogen peroxide decomposes slowly into water and oxygen gas.
2H₂O₂(aq) → 2H₂O(l) + O₂(g)

The reaction is catalyzed by light, because light supply energy for the decomposition. Therefore, hydrogen peroxide is protected from light by putting it in dark brown opaque containers.

light breaks down the hydrogen peroxide


The UV/H2O2 system is an advanced oxidation process (AOP) in which hydrogen peroxide (H2O2) is added in the presence of ultraviolet (UV) light to generate hydroxyl radicals (·OH). The oxidation potential of a hydroxyl radical (2.8V) is much greater than other oxidizing agents such as ozone (2.07V) and chlorine (1.39V) and thus has the capability of oxidizing a variety of organic and inorganic contaminants. See the Ultraviolet Irradiation and Hydrogen Peroxide overviews for descriptions of those treatment processes. In the UV/ H2O2 process, H2O2 is applied ahead of UV so that H2O2-treated water is irradiated.

The UV/ H2O2 process is accomplished through two stages of oxidation. In the first step, UV light catalyzes the dissociation of hydrogen peroxide into hydroxyl radicals through chain reactions. These oxidants then react with the contaminants of interest in the water. This technology has been shown to be effective in destroying many micropollutants present in the groundwater (e.g., MTBE, perchlorate, pesticides, 1,4-Dioxane, etc.) and surface water (pharmaceutical and personal care products, taste and odor compounds such as MIB and Geosmin) through direct chemical oxidation. The hydroxyl radical can be generated using either low-pressure (LP) or medium-pressure (MP) continuous UV light in the presence of H2O2. Low pressure high output (LP-HO) lamps are preferred when continuous contaminant removal is required (e.g., MTBE and perchlorate removal). MP lamps are recommended for periodic events (such as taste and odor (T&O) or pesticides). LP-HO lamps use less power and have lower operating temperatures (i.e., lower temperatures produce less scaling of sleeves) than MP lamps.

the proxide naturally wants to breakdown into water. uv light and heat accelerate transition. part of it is also probably purely cosmetic since most people associate brown/tan products with "medicines". higher concentration peroxides breakdown much more rapidly too, it's not as much a problem with your typical retail level 3% peroxides. but when you get to 7% and above stability is a real issue.

The obvious answer would be that sunlight chemically reacts to hydrogen peroxide and lessens the effectiveness

retard light induced degradation; same reason prescription bottles, beer bottles, and other containers are amber color