All-Purpose Home Cleaner Refill Tablets are naturally shelf-stable without the need for preservatives. Preservatives are “natural or synthetic compounds that help slow or prevent bacterial growth in a wide range of products, including foods, medicines and personal care products.” Bacterial growth is common in products which have water as a primary ingredient, such as liquids and gels. All of our products are concentrated dry powders or solid soaps that do not require added preservatives.