The skin protectant will be applied on clean and dry skin. It contains 95% paraffin oil and creates a hydrophobic layer on the skin surface.

The presence (no or yes) of erosion is defined according to the latest International League of Dermatological Societies glossary of cutaneous lesions as a loss of either a portion of or the entire epidermis. Number of subjects developing erosions of all subjects (cumulative incidence).

The presence (no or yes) of maceration is defined as the result of prolonged exposure (of the skin) to moisture and causes the skin to soften and breakdown so that the connective fibres can be teased apart and the skin often exhibits a white appearance. Number of subjects developing maceration of all subjects (cumulative incidence).

Numeric Rating Scale (NRS) pain score. The NRS ranges from 0 (no pain) to 10 (worst possible pain). Higher scores indicate greater pain severity. The NRS was administered only to participants without cognitive impairment (MMSE ≥24).

IAD related itch will be reported directly by patients (yes or no). Number of subjects reporting itch of all subjects (cumulative incidence).

The presence of local intolerances will be assessed with the following options:

(0) None;

1. homogeneous redness with scattered papules;
2. homogeneous redness and homogeneous infiltration
3. homogeneous redness and infiltration with vesicles
4. homogeneous redness and infiltration with coalescing vesicles

AEs and SAEs will be documented and reported according to the current regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices (MDR) Article 2.

Incidents abd serious incidents will be documented according to the definition of the EU regulation 2017/745 MDR Article 2 and reported to the Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM).

In the control group, standardized mild skin cleansing regimen without application of an additional skin protectant will be conducted by nursing staff.

Total of all reporting groups

Race and Ethnicity were not collected from any participant.

Degree of care dependency according to the German Social Code Book XI (SGB XI). Care levels range from 1 to 5, with higher levels indicating greater impairment and care dependency. Care levels were obtained from existing patient/resident records.

Care level 1: minor impairments of independence or abilities Care level 2: substantial impairments of independence or abilities Care level 3: severe impairments of independence or abilities Care level 4: most severe impairments of independence or abilities Care level 5: most severe impairments of independence or abilities with special nursing needs

Study-relevant main diagnosis categories at baseline

Mini-Mental State Examination (MMSE) total score. The MMSE is a 30-point structured cognitive test assessing overall cognitive function. Total scores range from 0 to 30, with higher scores indicating better cognitive performance and lower scores indicating greater cognitive impairment. The total score is calculated by summing item scores. Scores are commonly interpreted as follows: 24-30 within the normal cognitive range; 19-23 mild cognitive impairment; 10-18 moderate cognitive impairment; 0-9 severe cognitive impairment.

Number of individuals with scores ≥ 24 (cognitively intact or mildly impaired) and < 24 (cognitive impairment)

The Barthel Index was used to assess functional independence in activities of daily living (range 0 to 100), with higher scores indicating greater independence

Baseline IAD status was assessed using the Ghent Global Incontinence-Associated Dermatitis Categorisation Tool (GLOBIAD); participants presented with either no IAD or mild IAD (category 1A) at baseline.

Anatomical location of IAD category 1A among affected participants at baseline (front, back, or both).

This row includes only participants with IAD category 1A at baseline (24/167); therefore, the numbers reflect a subgroup of the total study population rather than the full sample.

Severity of erythema (none/pink/red) was assessed based on the redness item by Borchert et al. (2010).

This row includes only participants with IAD category 1A at baseline (24/167); therefore, the numbers reflect a subgroup of the total study population rather than the full sample.

Presence of skin maceration among participants with IAD category 1A at baseline was documented by location (front or back)

This row includes only participants with IAD category 1A at baseline (24/167); therefore, the numbers reflect a subgroup of the total study population rather than the full sample.

IAD-related itch among participants with IAD category 1A at baseline was documented.

This row includes only participants with IAD category 1A at baseline (24/167); therefore, the numbers reflect a subgroup of the total study population rather than the full sample.

IAD-related pain among participants with IAD category 1A at baseline was documented.

This row includes only participants with IAD category 1A at baseline (24/167); therefore, the numbers reflect a subgroup of the total study population rather than the full sample.

Erythema intensity was measured at a standardized site in the sacral region using an objective skin color measurement device (Mexameter MX 18, Courage + Khazaka) and expressed in arbitrary units (AU), with higher values indicating greater redness.

Participant satisfaction with incontinence care was assessed using a numerical rating scale ranging from 0 (not satisfied at all) to 10 (very satisfied).

In the intervention group II, standardized mild skin cleansing regimen and daily topical application of a hydrophobic skin protectant at the exposed skin areas will be applied by nursing staff.

In the control group, standardized mild skin cleansing regimen without application of an additional skin protectant will be conducted by nursing staff.

Erythema measured with the Mexameter MX® 18 (Courage + Khazaka, Cologne, Germany). Means of two duplicate measurements per skin area are displayed in arbitrary units (AU) ranging from 0 (= no erythema) to 999 (= extreme erythema).

Participant numbers vary across study days because instrumental erythema measurements were analyzed per visit based on available data. At some visits, assessments were not possible for individual participants (e.g., temporary absence or medical reasons), but measurements were performed again at subsequent scheduled visits. Therefore, denominators may decrease or increase between days and reflect available observations at each time point rather than the total study population.

Clinical rating of erythema is conducted according to the item 'Redness' of the incontinence-associated dermatitis and its severity (IADS) instrument. The 3-Item-Scale describes 'Redness' as (1) none, (2) pink, (3) red/ bright red.

Rows include only participants with IAD at the respective follow-up visit, as erythema was assessed as an IAD-related sign. Therefore, denominators differ from the total study population and reflect only those with present IAD at that time point.

The presence (no or yes) of erosion is defined according to the latest International League of Dermatological Societies glossary of cutaneous lesions as a loss of either a portion of or the entire epidermis. Number of subjects developing erosions of all subjects (cumulative incidence).

These rows include only participants with IAD at the respective follow-up visit, as erosion was assessed as an IAD-related skin sign. Therefore, denominators differ from the total study population and reflect only those with present IAD at that time point.

The presence (no or yes) of maceration is defined as the result of prolonged exposure (of the skin) to moisture and causes the skin to soften and breakdown so that the connective fibres can be teased apart and the skin often exhibits a white appearance. Number of subjects developing maceration of all subjects (cumulative incidence).

Rows include only participants with IAD at the respective follow-up visit, as maceration was assessed as an IAD-related skin sign. Therefore, denominators differ from the total study population and reflect only those with present IAD at that time point.

Numeric Rating Scale (NRS) pain score. The NRS ranges from 0 (no pain) to 10 (worst possible pain). Higher scores indicate greater pain severity. The NRS was administered only to participants without cognitive impairment (MMSE ≥24).

Only participants without cognitive impairment (MMSE ≥24) were eligible for assessment using the Numeric Rating Scale (NRS). At Day 6, 2 of 20 participants with IAD met this criterion; at Day 14, 3 of 8 participants with IAD met this criterion. Therefore, denominators differ from the total study population and vary by follow-up visit.

IAD related itch will be reported directly by patients (yes or no). Number of subjects reporting itch of all subjects (cumulative incidence).

Rows include only participants with IAD at the respective follow-up visit, as itch was assessed as an IAD-related symptom. Therefore, denominators differ from the total study population and reflect only those with present IAD at that time point.

The presence of local intolerances will be assessed with the following options:

(0) None;

1. homogeneous redness with scattered papules;
2. homogeneous redness and homogeneous infiltration
3. homogeneous redness and infiltration with vesicles
4. homogeneous redness and infiltration with coalescing vesicles

No adverse events (AEs) or serious adverse events (SAEs) occurred during the study. Safety monitoring was performed throughout the trial, and all scheduled assessments confirmed the absence of AEs and SAEs; therefore, all entries are zero.

AEs and SAEs will be documented and reported according to the current regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices (MDR) Article 2.

Incidents abd serious incidents will be documented according to the definition of the EU regulation 2017/745 MDR Article 2 and reported to the Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM).

In the intervention group II, standardized mild skin cleansing regimen and daily topical application of a hydrophobic skin protectant at the exposed skin areas will be applied by nursing staff.

In the control group, standardized mild skin cleansing regimen without application of an additional skin protectant will be conducted by nursing staff.