A Brief and Simple Chemistry Lesson in Soap Composition

All these years, I have been using and recommending soap, but I’ve only had a vague notion of its chemical composition and how it works. I decided to do some research into the topic of soap composition so that I could better explain to patients what it does.

I found out that soap is made by adding sodium hydroxide (lye dissolved in water) to animal or vegetable fats. As a result, there is a chemical reaction called saponification. Fatty acids release from the oily and fatty structure, binding with the sodium. The resulting fatty acid salt is soap as we know it.

Soap composition is just the first part; the second and equally important aspect is how it cleans. When soap cleans, a complex chemical process ensues. When water and soap “mix”, the sodium component is water soluble, but its fatty acid component is hydrophobic and will not dissolve in water. This property of soaps creates a structure called a micelle, which is essentially a cell-like structure with a soap membrane. You can see this phenomenon at work when you add soap to a greasy pan with water in it. These micelles bind dirt, oil and grease which we can then wash off with warm water. This is the essence of the cleaning process.



What Are The Mechanics of a Sulfa Allergy? How Is It Managed?

Recently, a patient had a complex allergic reaction in the form of a rash. I was quite stymied in figuring out what was causing it. Ultimately, I identified her thiazide diuretic as the culprit, specifically the sulfonamides in it. Sure enough, the rash cleared when she discontinued the medication.

A few weeks ago, the patient’s husband asked me, “what is the mechanism of a ‘sulfa allergy’? Does it mean [his wife] can never take a sulfur-based medication again?” I didn’t know the answer to his questions, as I had never given the subject much thought. Thus, I became curious and did some research into the topic.

I discovered that, in most cases, the patient is allergic to sulfonamide medications exclusively. A sulfa allergy doesn’t mean an adverse reaction to everything containing sulfur (such as food products). Sulfur itself is present in most proteins and genetic material. Furthermore, sulfur is an essential component to environmental functions such as the global sulfur cycle.

Conversely, sulfonamides are the molecules only used in medications. There are two classes of sulfonamide medications: antimicrobial and non-antimicrobial. The former is the more allergenic of the two. A sulfa allergy is pretty rare, affecting only 3.4% of the population. 

Patients who are very sensitive to sulfonamides (e.g. HIV patients) have an increased concentration of reactive metabolites. So do people with slower drug metabolism (slow acetylators). Metabolites are the byproducts of the liver’s partial breakdown of sulfonamide. This process can bind proteins in the serum and become “immunogenic”. 

What are the risks of non-antimicrobial sulfonamides? These medications (loop diuretics, sulfonylureas, dapsone) seem less likely to produce an immune system response. If a patient is allergic to sulfonamide antibiotics, the non antibiotics are not necessarily unsafe to use. But in cases where severe reactions occur, use caution. The same holds true for patients allergic to non-antimicrobial sulfonamides: discontinue use if you have a severe reaction.

The Bugs Are Out! How Can I Prevent Mosquito Bites?

Nothing gets people racing for cover quite like “the bugs are out.” Not only do mosquito bites cause itchiness and swelling, but they also put you at risk for mosquito-borne illnesses. These include malaria, West Nile virus, and Eastern equine encephalitis (aka “Triple E”).

Preventative Measures

Luckily, there are several ways to prevent mosquito bites. Preventative methods usually come in sprays, which contain DEET, Icaridin, and oil from lemon eucalyptus. DEET is the longest lasting repellent, and can be found in repellent brands such as OFF. When applying repellent, follow the “spray it, don’t say it” rule: keep your eyes and mouth shut.

Dress to protect. Wear long pants and long sleeves. Close-toed shoes are the best option, especially if you’re hiking, biking, or walking long distances. You may also want to wear a hat that covers your ears. Some hats even come with mosquito netting so you can cover your face.

Know where the vermin are setting up shop. Mosquitoes typically live in warm, damp environments with a lot of vegetation, such as swamps and marshes. If you’re going to be near those kinds of areas, make sure that you spray repellent generously every couple of hours. Mosquitoes tend to come out at dusk, so move things indoors when the sun starts to set.

If You’ve Already Been Bitten

If you’ve already been bitten, you may start to notice itchiness, swelling, and redness around the site of the mosquito bite. Most of these symptoms manifest the day after, and clear up within a few days. However, they can intervene with daily life, and some are severe enough to warrant a visit to the doctor.

Mosquito bites manifest most commonly in the form of an itchy bump that is hard to the touch. Apply a hydrocortisone ointment to the site to relieve itching and swelling. Calamine lotion for mild itchiness is also a good option. All of these are available as an OTC medication; you can find them at any pharmacy or supermarket. Other options for relief are cold compresses and OTC oral antihistamines such as cetirizine.  

Do not scratch or pick at the bite. This will only delay the healing process. Furthermore, it can lead to infection and scarring. If you think that this may be a problem, cover the site with liquid bandaid.


Mosquito bites. Mayo Clinic. http://www.mayoclinic.org/diseases-conditions/mosquito-bites/basics/definition/CON-20032350?p=1. Published October 22, 2015. Accessed June 13, 2017.


Tar Products Can Pave the Way to Healthier, Clearer Skin

Dermatologists have always been using tar products to treat skin diseases. For example, tar is an essential part of psoriasis therapy, either on its own or combined with ultraviolet light. Dermatologists also use it to treat eczema, though this is less common.

I’ve stopped recommending tar products in my practice, mostly because it’s OTC and I’ve forgotten about it. There is also an unproven concern that it can cause cancer, which is (understandably) a large deterrent. Furthermore, patients do not appreciate its pungent smell.

So when patient recently asked me about how my recommendation of tar products worked, I really didn’t have a clear answer. Thus, I did some research into the subject and learned some interesting things.

First, what makes up tar? Tar is a broad term that refers to organic plant matter that can occur naturally. You’ll find tar most commonly in pits, where you’ll will also find pitch and asphalt. One can also create tar-like products by dry heating coal to about 1200ºC. At this temperature, the coal melts into a thick liquid called crude coal tar.

Crude coal tar contains an estimated 10,000 high molecular weight hydrocarbons and aromatic (aka “odorous”) polycyclic hydrocarbons. These specific aromatic polycyclic hydrocarbons may help treat skin diseases.

Second, how do tar products interact with skin cells? Skin cells (keratinocytes) absorb and break down these aromatic polycyclic hydrocarbons using the same system that breaks down natural plant flavonoids. (Flavinoids are ubiquitous pigments in plants. Research indicates they have health benefits).

Furthermore, there is some research to suggest that the aromatic polycyclic hydrocarbons can help the barrier function in atopic dermatitis normalize. It may also help block the effects of inflammation in this particular disease.

In conclusion, I can now recommend tar products to patients with more confidence. It comes in useful for patients as an alternative to topical steroids, and for maintenance of stable chronic skin diseases.


From Feldman et al UpToDate


Wikipedia for “tar” and flavonoids


The Reason Behind Most Urticaria Cases is Unknown

Urticaria (chronic hives) is one of the most interesting skin problems because most case causes go unidentified. Though there are several categories of causes (prescription medication, OTCs, foods, physical factors, immunologic and infectious), the reason behind 70-80% of cases is unknown.

In one recent case, a female patient related a 20+ year history of hives at different points in her life. Most of her incidences had occurred around pregnancy. Her hives had recently been acting up, and it turned out her implantable progesterone eluting IUD had been replaced a few months prior.

In medical literature and research, about 5% of women develop urticarial and even lip swelling (angioedema) in reaction to oral contraceptives. This female patient’s case may one of the rare instances where a cause was identified.


Bingham CO. New-Onset Urticaria. Saini S, Callen J, Feldweg AM, eds. UpToDate.


Cranial Facial Hyperhidrosis: Excessive Sweating that Dampens Daily Life

A patient recently came to me with complaints of excessive sweating from the scalp. This is an unusual form of hyperhidrosis called cranial facial hyperhidrosis. It is similar to people who have sweaty palms and sweaty armpits.

In this particular patient’s case, it was interfering with the quality of their life. It was not related to their being overheated, and it was getting worse. The patient did not want to have an excessively sweaty scalp for no reason at all.

I’ve been consulting with this patient’s internist on the best course of treatment. I will most likely prescribe an oral agent called Glycopyrrolate.

Cases of Shingles in Children is Rare But Not Impossible

Recently, a pediatrician consulted me on a 13 year old with shingles. The patient had been vaccinated with the live attenuated vaccine as a younger child. Patient responded nicely to a course of valacyclovir (antiviral medication).

The case got me thinking about two things: first, in my experience, shingles in children is very unusual. Epidemiologic data supports the rarity to about 1 case for every 1000 people aged 1-25 per year.

Second, it got me thinking about the pathogenesis (how the process works). It must be that the latent live attenuated virus can set up shop in the spinal cord. Over time, the patient’s ability to detect varicella zoster may wane. In these cases, the virus escapes local control, resulting in findings called shingles.

This patient’s pediatrician and I ran the case by an infectious disease specialist. The specialist thought that it would be wise to check the patient’s CBC, specifically the lymphocyte count. We wanted to make sure there were no underlying conditions.


Albrecht MA. Epidemiology and pathogenesis of varicella-zoster virus infection: Herpes zoster. Hirsch MS, Mitty J, eds. http://www.uptodate.com/contents/epidemiology-and-pathogenesis-of-varicella-zoster-virus-infection-herpes-zoster?source=search_result&search=Epidemiology and pathogenesis of varicella-zoster virus infection%3A Herpes zoster&selectedTitle=1~150. Accessed May 19, 2017.

Certain Oral Contraceptive Brands Can Worsen Acne and Hair Loss

Oral contraceptives are an established part of acne management, especially in post adolescent women. However, I have seen a few cases where some oral contraceptive brands exacerbate acne and hair loss.

The progesterone components of some OCPs have androgenic (testosterone-like) properties. Androgenic properties can make acne worse. For example, they can cause hair loss in individuals genetically vulnerable to alopecia. I have been recommending orthotricyclen with 35 micrograms of estrogen for female adult acne patients for years. But I failed to realize that the progesterone component is less androgenic.

While reviewing a recent case of a young patient with significant alopecia, further history revealed that she had been on oral contraceptives for years. I had done a full work up on her three years ago, but failed to get the history of birth control use. Some patients don’t consider it a medication. The progestin in this particular brand is in the mid range of androgenicity; it has been associated with hair loss in about 2% of women. I have contacted this patient’s PCP to see if she can be prescribed a contraceptive with less androgenicity.



Osathanondh, R, Stelluto, MR, Carlson, KJ. Contrception. In: Primary Care of Women, Carson KJ, Eisenstadt(eds), Mosby, St. Lois, 1995. In UptoDate

What Is In Sunscreen And What’s the Best Way to Use It?

My advice to all patients is to use sunscreen (SPF 50), which is available at most stores. Apply to the face, ears, back of the neck, hands, exposed legs, and feet. Reapply ever two hours, and immediately after sweating or water exposure.

It’s important to know the key ingredients in the sunscreen product itself, and how safe they are.

Zinc oxide and Titanium oxide are common ingredients found in many products. These micronized particles are for the most part safe, and don’t penetrate unbroken or undamaged skin. However, there are some concerns about these substances being absorbed into damaged areas. They should be avoided when the skin barrier is impaired. For example, if you have eczema or even a sunburn, don’t apply sunscreen directly to the wound site. Make sure you have an alternative method of protecting the site.

Products that contain benzophenone pose risks to the environment: they are harmful to coral reefs. They may also cause hormone complications: theoretical absorption may lead to estrogen-like effects, based on a rodent study. Benzophenone is most commonly found in organic sunscreens.

How you apply sunscreen has a direct effect on how well you are protected. While using sunscreen:

  • Apply generous amounts of sunscreen fifteen minutes before going outside. For optimal protection, apply your sunscreen before you get dressed.
  • It’s important to reapply every two hours, and to do so immediately after swimming or excessive sweating, even if the bottle promises water resistance.
  • Just because it’s cloudy doesn’t mean you don’t have to sunscreen. Clouds don’t protect you from damage, as UV light passes through them. Apply sunscreen as you would if it were sunny.
  • Keep in mind that sand, water, and snow are reflective surfaces.

The sunscreen product itself doesn’t protect you from serious complications such as heat stroke and dehydration. Don’t stay in the direct sunlight for too long, drink plenty of fluids, and reapply.

Onycholysis: What Causes It and How Can It Be Treated?

I often see women with onycholysis, or peeling of the nails. I feel like they don’t buy into my standard explanation, which is that the most common cause is mild chronic trauma to the nails. Most seem to want a miracle lotion, or a prescription for anti-fungal medication, but this isn’t always the correct form of treatment.

Onycholysis occurs in the fingernails and toenails, when the nail plate begins to peel away from the nail bed. It’s characterized by a white sheen over the nail, which is the nail plate separating from the nail bed. In the fingernails, the cause is most often trauma from manicuring, picking, and occupational injuries. In the toenails, the most frequent source is pressure and friction from walking in close-toed shoes.

Most onycholysis patients are women, and the most common cause is irritation. As mentioned before, excessive nail filing and overexposure to chemicals in manicuring products can irritate the area and cause breakage. Sometimes, a patient can even have an allergic contact dermatitis reaction to the adhesives in acrylic nails. In rare cases, onycholysis indicates iron deficiency anemia or an overactive thyroid.

To treat onycholysis, clip off the unattached parts of the nail. Keep your fingers away from water unless absolutely necessary. Use gloves when cleaning dirty surfaces, so that bacteria can’t get underneath your nails. Gloves also prevent mechanical injuries. Some even suggest using a hair dryer to blow your fingers dry, or just letting your hands air dry. Make sure you don’t cover or bandage the nails, as fungus and bacteria thrive in closed, moist areas. In more severe cases, you may need to get a prescription from a doctor.

In conclusion, if you have onycholysis, the key is to keep everything clean and dry. Thus, bacteria and infection have a minimal chance of finding a place to grow.  


Onycholysis – American Osteopathic College of Dermatology (AOCD). Onycholysis – American Osteopathic College of Dermatology (AOCD). http://www.aocd.org/?page=onycholysis. Accessed August 16, 2016.

Result Filters. National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/pubmed/25512134. Accessed August 16, 2016.