**12. Side effects and contraindications**

Reviewing the literature, we can find some described adverse effects, especially with the oral intake of high amounts of vitamin C.

Some of them are nausea, vomiting, heartburn, colic, diarrhea, and oxalate kidney stones in predisposed patients, and with intakes above 3000 mg/day [45], although at this point, there is no unanimity among the different bibliographies [46].

Cases of topical vitamin C contact dermatitis have been reported in patients who tolerated it perfectly orally [47].

Oral vitamin C supplementation during pregnancy decreases the risk of placental abruption by 36%. Vitamin C is not teratogenic and its topical use is not contraindicated in pregnancy, and the associated use of sunblock is recommended on a daily basis, as the hormonal influence on melanogenesis was already discussed in a previous section [48]. In the case of pregnancy, it is vital to prevent the appearance of melasma, which can appear in up to 75% of women in the gestational state [49].
