Dairy and nightshades are among the most frequently discussed dietary triggers in HS online communities. Many patients report that eliminating one or both improved their symptoms. But what does the scientific evidence actually show? This article reviews the current research and provides practical guidance for patients considering elimination trials.
Dairy and HS: The Evidence
The proposed mechanism for dairy's effect on HS centers on insulin-like growth factor 1 (IGF-1). Dairy products, particularly milk, stimulate IGF-1 production, which in turn activates the mTORC1 signaling pathway. mTORC1 promotes sebocyte proliferation and increases androgen signaling in the pilosebaceous unit, the same hair follicle structure that is the primary site of HS pathology.
A 2019 patient survey published in the Journal of the American Academy of Dermatology found that 38% of HS patients who tried dairy elimination reported improvement. A smaller Italian study found that patients who reduced dairy intake had lower IHS4 scores (a validated HS severity measure) after 12 weeks compared to controls. These are observational findings, not randomized trial data, but the IGF-1 mechanism is biologically plausible and consistent with the known role of hormonal signaling in HS.
If you decide to trial dairy elimination, the key foods to avoid are cow's milk, cheese, yogurt, butter, cream, and ice cream. Goat's and sheep's milk products contain lower levels of IGF-1-stimulating proteins and may be better tolerated by some patients, though evidence for this is limited. Plant-based milks (oat, almond, soy, coconut) do not stimulate IGF-1 and are generally considered safe alternatives.
Nightshades and HS: The Evidence
Nightshades (tomatoes, peppers, eggplant, potatoes, and tobacco) contain alkaloids including solanine and capsaicin, which some proponents claim can increase intestinal permeability and trigger systemic inflammation. The nightshade-HS connection is almost entirely based on patient anecdote and online community reports. There are no published clinical studies specifically examining nightshade elimination in HS patients.
The evidence base for nightshade elimination in HS is substantially weaker than for brewer's yeast or dairy. Nightshades are nutritionally valuable foods, and eliminating them without a clear personal trigger response means giving up significant dietary variety and nutritional benefit for uncertain gain. The current consensus among HS nutrition researchers is that nightshade elimination is not a first-line dietary recommendation for HS.
Practical Guidance: How to Identify Your Personal Triggers
Rather than eliminating multiple food groups simultaneously, a structured single-food elimination approach is more informative. Start with brewer's yeast (the best-supported trigger), eliminate it strictly for 12 weeks, and track your symptoms. If you see improvement, you have identified a likely trigger. If you see no change, move on to dairy elimination for another 12 weeks. Only consider nightshade elimination if you have a strong personal suspicion based on your own symptom patterns.
Keep a detailed food and symptom diary throughout any elimination trial. Note what you eat, when new lesions appear, pain levels, and drainage. This diary will be valuable both for identifying your personal triggers and for discussing dietary management with your dermatologist.