Soap has been used for personal hygiene for thousands of years. And cleaning the skin also plays an important role in veterinary medicine - especially for dermatological problems. But what exactly is the difference between traditional soap and the modern detergents we often encounter in skin shampoos? And as a veterinarian, how do you make an informed choice in what to recommend?

The origin of soap

The history of soap goes back thousands of years. Originally, soap was made by mixing fats or oils with the ashes of burnt plants. In ancient Babylon, Egypt and Rome, this mixture was already being used to cleanse skin and clothing. Only later was soap linked to personal hygiene - in part due to the insights of doctors such as Galenus.

After a period of decline in the Middle Ages, when washing was considered immoral, soap returned to the scene in the 18th and 19th centuries. Thanks to scientific discoveries about bacteria (Pasteur) and industrial progress, soap became a widely accessible hygiene product.

How does soap work?

Soap is a surfactant (surfactant) that can mix water and grease. Chemically, a soap molecule consists of:

• A hydrophilic cup (water-attracting)
• A hydrophobic tail (grease-dissolving)

When soap comes in contact with skin, grease and water, the grease-dissolving tails bind to dirt or sebum. The water-loving heads keep it completely soluble, effectively washing away dirt.

Soap vs. detergent: what's the difference?

Although we often talk about "shampoo" in the consulting room, many modern cleaning products are not soap but rather detergents - synthetic cleaners based on petrochemicals.

Key differences:

Aspect	Soap	Detergent
Provenance	Natural (fats + lye)	Synthetic (petrochemical origin)
Operation in hard water	Forms precipitation, loses action	Works well even in hard water
Cleaning power	Mild, suitable for sensitive skin	Stronger, more effective on grease & grime
Skin Load	Less irritating, more skin-friendly	Can be drying, depending on composition

When do you choose what?

• Soap is milder and thus suitable for sensitive skin types or as an after-treatment when restoring the skin barrier.
• Detergents are more effective in cases of severe contamination or conditions requiring removal of fat or microorganisms (e.g., pyoderma, Malassezia).

So the choice depends on the purpose of cleaning, the skin condition, and any underlying dermatological conditions.

Soap in shampoos: still relevant?

Although soap was historically an essential cleansing agent, in modern veterinary care it is still mainly used in niche applications - such as natural, gentle cleansing or for specific skin types. Most animal shampoos are based on mild detergents, often combined with moisturizing or conditioning additives such as:

• Glycerin
• Oatmeal extract
• Ceramides
• Allantoin

This combination provides balanced cleansing without further drying or irritating the skin.

Conclusion

Soap remains a fascinating product with a long history. In veterinary medicine, the move to synthetic detergents makes sense because of their effectiveness, especially in pathology. Yet understanding the differences is essential to provide targeted advice: when mild cleansing is needed, when vigorous cleansing is desired - and most importantly, how to balance the animal's skin health.