Natural deodorants have surged in popularity as people seek alternatives to traditional antiperspirants. Many of these formulations contain sodium bicarbonate, commonly known as baking soda, which is highly effective at managing underarm odor. However, the use of baking soda in deodorant is controversial due to its potential to cause adverse skin reactions. The main concern centers on localized skin irritation and the disruption of the skin’s protective barrier when applied to the sensitive underarm area.
Alkalinity and Skin Reaction
The surface of healthy skin maintains a slightly acidic environment, known as the acid mantle, which typically ranges in pH from 4.5 to 5.5. This acidity acts as a protective barrier, helping to maintain the skin’s moisture and supporting beneficial microbiota. Sodium bicarbonate is notably alkaline, with a pH of approximately 8.3 to 9.0 when dissolved in water.
Applying a substance with such a high alkaline pH disrupts the natural acid mantle. This significant pH mismatch compromises the skin’s barrier function. The result is often contact dermatitis, a type of irritation characterized by redness, stinging, flaking, and an itchy rash.
For individuals with sensitive skin, the irritation can be particularly pronounced. Shaving causes micro-abrasions that make the skin more vulnerable to the alkaline substance, increasing the risk of a severe reaction.
Mechanism of Odor Control
Baking soda is included in natural deodorant formulations due to its potent ability to neutralize odor. Body odor is caused by the waste products of bacteria that thrive in the warm, moist environment of the armpit. These bacteria break down compounds in sweat, producing foul-smelling byproducts.
Sodium bicarbonate acts as a base, chemically reacting with and neutralizing the acidic compounds that cause malodor. The ingredient also creates an alkaline environment on the skin, which can inhibit the proliferation of some odor-causing bacteria.
This neutralizing action is distinct from how antiperspirants work, which typically use aluminum compounds to physically block sweat ducts and stop the flow of perspiration. Baking soda is a true deodorant, focusing on odor management rather than sweat reduction. Its effectiveness at eliminating smell is the primary reason it remains a popular component of many natural options.
Systemic Health and Absorption Concerns
A common worry among consumers is whether sodium bicarbonate applied to the underarms can be absorbed through the skin and cause internal health problems. Current scientific understanding suggests that systemic absorption from topical deodorant use is minimal and does not pose a risk of internal toxicity.
Studies investigating transdermal delivery of sodium bicarbonate, even in specialized lotions, have generally found no significant increase in blood bicarbonate levels or changes in systemic pH. The amount absorbed through the intact skin is negligible in the context of internal health.
Concerns about internal organ damage or systemic toxicity are typically related to the massive ingestion of baking soda, not to its external cosmetic use. While baking soda can cause significant localized irritation on the skin, it is considered safe from a systemic health standpoint when used as a deodorant. The adverse effects remain isolated to the surface of the skin.
Strategies for Safe Use and Alternatives
For individuals who tolerate baking soda well, or who find its odor-neutralizing power unmatched, using a minimal amount of product may help reduce the risk of irritation. Applying deodorant only to completely clean and dry skin, and avoiding application immediately after shaving, can also mitigate potential reactions. A simple patch test on a small area of the underarm is always advisable before committing to a new product.
For those who experience sensitivity, numerous effective baking soda-free alternatives are now widely available. Many alternative formulations rely on ingredients that still manage odor without the high alkalinity.
Effective alternatives include:
- Magnesium hydroxide, a gentle antacid that neutralizes odor-causing acids without significantly altering the skin’s pH.
- Zinc ricinoleate, which chemically traps odor molecules.
- Absorbent materials like activated charcoal and various clays.
These ingredients work to control moisture and bind to odor compounds, providing a functional, non-irritating solution for sensitive skin. Choosing a baking soda-free option allows consumers to maintain a natural routine without the risk of an alkaline-induced rash.