Hair Loss Treatment Side Effects | Local Versus Systemic

hair loss treatment side effects

So much nicer administering topical treatments … don’t you think?

Why Should I care?

The local versus systemic effects of a medicated hair loss treatment is an important concept to understand when considering hair loss treatment side effects and which one is right for you. Put simply, they can have a large bearing on the type and severity of any potential side effects.

Local Versus Systemic Effects Defined

A local effect essentially means that the action of the medication is limited to the location in which it is applied. Systemic effects occur when the medication impacts the systemic circulation, which supplies nourishment to all of the tissue throughout your body via the arteries, veins and capillaries (with the exception of the heart and lungs).

Right, So It’s Topical All the Way Then?

By definition, oral (and parenterally*) administered medications have systemic effects. That is, effects are felt at some distance from the site of administration by virtue of its entry into the blood or lymphatic supply. One might imagine that, conversely, topical medications applied to the skin will have only local effects; limited to the site of administration.**

Not necessarily so.

Being the well-researched bunch that you are, you will have guessed that even topical skin medications can give rise to systemic effects. Whilst topical medications designed for local effect can avoid unnecessary systemic absorption, and potential adverse gastrointestinal events, it is not a guarantee.

* Taken into the body or administered in a manner other than through the digestive tract, as by intravenous or intramuscular injection.

** Since currently available topical hair loss medications are applied directly to the scalp, for the purposes of this article, I’ve limited the discussion to topicals applied to the skin (drugs applied to the eyes or surface of a tooth, for example, are also considered to be topical).

What factors Impact the Level of Systemic Effects from Topical Medications

Whilst most topicals will rarely cause serious side effects, if used as instructed, there are a number of factors that can increase your risk, including:

  1. The strength, or potency
  2. The area of skin being treated: generally speaking the larger the area treated, the greater the risk
  3. The length of treatment: generally speaking the longer you use a topical, especially on a daily basis, the greater the risk
  4. Your age: young children and those aged over 70 have a greater risk as the skin tends to be thinner

What Can You Do to Minimise Adverse Reactions and Negative Side Effects?

Following the instructions for use is a good start. That said, you should aim to apply the smallest effective amount to minimise systemic absorption.

You can do this by starting with the recommended dose. If that achieves your desired result, start to gradually reduce the amount. Through trial and error, aided by careful observation, you may find that you can decrease application to a level well below the recommended amount. In my view it’s worth the effort to do this as an insurance policy against any potential negative side effects arising from systemic absorption longer term.

As I described in the ‘What Worked for Me’ section, I’ve used this approach to great effect when applying Minoxidil. I’m currently applying 0.5ml per day in the morning, down from the 2ml recommended when I started (1ml in the morning and 1ml in the evening as recommended at the time.

The above approach applies equally well to orally or parenterally administered medications.


If you’re not a big fan of using pharmaceuticals to treat your hair loss, or have a strong bias towards minimizing potential hair loss treatment side effects in any pharmaceutical treatment you do choose, you’ll likely want to try topical products in the first instance. If this is the case, you’ll certainly be moving propecia (finasteride) lower down your list than, say, Minoxidil.

Just remember, however, that topical application does not necessarily guarantee ‘local only’ impact. Although topicals will normally have far lower systemic effects, it does not automatically mean that the product is safe for you. For example, you may have an unrelated condition that could be aggravated by the topical entering the systemic circulation.

Whilst an understanding of topical versus systemic effects should give you a good indication of the likely type and severity of side effects, ultimately the best indication is through research on the side effects themselves, coupled with a consideration of your own physiology and any known health issues. Include your doctor in the conversation if you’re unsure.

The bottom line is that although it’s tempting to take a ‘get my hair back at whatever cost’ approach, a consideration of hair loss treatment side effects should be a part of everyone’s decision-making process.

To see what worked for me go here.

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Photo credit: derekwt via photopin cc


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