Pantothenic Acid as an Unexpected Cause of Hypersensitivity to Sensitive or Atopic Skin Care Products—A Narrative Review

Pantothenic acid (PA; vitamin B5) is an essential component of many key metabolic processes. Vitamin B5 deficiency causes dysfunction in various systems and organs. Humans do not produce vitamin B5, so it must be constantly replenished through diet or supplementation. Pantothenic acid is synthesized by plants, fungi, and bacteria, so a well-balanced diet is a good source of pantothenic acid. Pantothenates have beneficial effects on the skin (regenerative, healing, and anti-inflammatory effects). They are readily absorbed through the skin, making them a common active ingredient in cosmetics and medications with soothing, healing, regenerative, moisturizing, and protective properties for damaged, sensitive, or atopic skin, including topical products labeled hypoallergenic or specifically intended for people with sensitive skin. Although PA is considered non-allergenic and safe, paradoxically, frequent exposure, especially to damaged skin, appears to lead to hypersensitivity to this substance. The pathogenetic mechanisms of pantothenate hypersensitivity have not been clearly defined. The main sensitization pathway is likely a delayed cellular mechanism (type IV, contact). However, other types of hypersensitivity, including immediate (type I) and mixed mechanisms, cannot be ruled out. PA allergy is considered rare and therefore difficult to diagnose. This is due to the unexpected sensitizing factor and the lack of standard diagnostic tests. Due to the likely contact nature of the allergy, patch testing (PT) with a cosmetic (drug) provided by the patient (“as is”) and PA (5% in petrolatum; 5% PET) appears to be the best approach. It is also suggested that PA (5% PET>) be included in the standard series of allergens (haptens) used in routine PT diagnostics. It appears that PA allergy is more common than currently believed, particularly in people with atopic skin and polysensitized individuals, who are the primary users of products containing pantothenate. It is possible that in these individuals, pantothenic acid may be more harmful than beneficial.