Botulinum toxin A (BTX) and microwave thermolysis (MWT) are standard axillary hyperhidrosis treatments, but comparison of their subclinical effects is lacking. Line-field confocal optical coherence tomography (LC-OCT) is a promising non-invasive imaging tool for visualizing tissue-interactions. This study aimed to describe subclinical effects of BTX and MWT for axillary hyperhidrosis with LC-OCT-imaging compared to histology. This study derived from an intra-individual, randomized, controlled trial, treating axillary hyperhidrosis with BTX versus MWT. Subclinical effects based on LC-OCT images from baseline and 6-month follow-up (n = 8 patients) were evaluated and compared to corresponding histological samples. At baseline, LC-OCT visualized eccrine pores at the skin surface and ducts in the upper dermis (500 μm), but not deeper-lying sweat glands. Histology identified entire sweat glands. Six months post-treatment, LC-OCT revealed no detectable morphology changes in any BTX-treated axillae (100%), while recognizing obstructed eccrine pores and atrophy of eccrine ducts in most MWT-treated axillae (75%). Histology corroborated LC-OCT findings, while also showing substantial changes to entire sweat glands. LC-OCT enabled visualization of subclinical alterations of superficial eccrine ducts after MWT and unchanged morphology after BTX. LC-OCT is a promising tool for non-invasive assessment of treatment-specific tissue-interactions that can be complementary to histology.

The popularity of tattoos has led to an increase in associated skin reactions, including complications such as infection, allergic reactions and rare conditions such as tattoo-induced cutaneous lymphoid hyperplasia (CLH). CLH is a benign lymphoproliferative reaction with clinical features resembling malignant cutaneous lymphomas. Non-invasive diagnostic tools like reflectance confocal microscopy (RCM) and the new line-field confocal optical coherence tomography (LC-OCT) are being studied in dermatology better to understand the morphological patterns of many dermatological diseases. Between September 2021 and May 2023, patients with suspicious lesions for tattoo-related CLH were analysed using RCM and LC-OCT before confirming the diagnosis of CLH through skin biopsy and histopathological examination. The study included five cases of CLH. It focused on the analysis of high-quality LC-OCT images/videos and RCM images to investigate the features of CLH in tattooed individuals. Most (80%) cases exhibited a mixed T and B lymphocyte infiltration subtype, while 20% showed a predominant T infiltration subtype. RCM and LC-OCT revealed characteristic features, including architectural disarray, fibrosis, lymphoid infiltrates, and pigment deposits in the epidermis and dermis. Non-invasive tools such as RCM and LC-OCT are valuable in diagnosing tattoo-related CLH. While skin biopsy remains the current standard for diagnosis, RCM and LC-OCT can serve as helpful adjuncts in identifying the most representative area for biopsy. They may potentially become alternative diagnostic options in the future, offering benefits in terms of cost, diagnostic efficiency, aesthetics and patient satisfaction as the prevalence of tattoo-related adverse reactions continues to rise.