Diagnosing Hair Loss: Understanding The "H.A.I.R." Principle

So, what' s my diagnosis ?

I enjoy participating in a number of online forums, including those where I answer questions from individuals with hair loss. It's challenging to offer any valuable information about diagnosis with questions that offer 1 or 2 sentences about a patient's hair loss. Sometimes it's even challenging with a photo. 

Years ago in my teaching clinic, I came up with a 4 letter memory tool to teach doctors in training about the proper steps needed to diagnose hair loss. The first letter of teach of the key steps spells HAIR:


H = History

A= Assessment

I = Investigations

R= Repeat if necessary



The history of a patient's hair loss is extremely important and can't be ignored. All aspects are important including when it first occurred, how long it's been present, symptoms that accompany the hair loss (scalp itching, burning or pain), medications used by the patient, family history of hair loss, personal history of any medical conditions. All these things could be important to a patient's hair loss and need to be uncovered. 



A proper assessment of the scalp involves an "up close" exam. Sometimes this is not possible and photos need to suffice. But to be confident in what's causing a person's hair loss, the scalp needs to be examined. One can't stand across the room. One needs to look - and the closer the better!

It's important to examine exactly where the hair loss is occurring. Is it occurring in the frontal area? The top of the scalp? The middle? the back? Is there redness? Is there scarring? 


I= Investigations.

A variety of investigations need to be considered in anyone with hair loss. These include blood tests, biopsy and collection of shed hairs. It doesn't mean that all these are necessary - it just means they need to be considered. 

For all women with hair loss, I advise three tests: complete blood counts (CBC for hemoglobin), thyroid studies (TSH test) and iron studies (ferritin test). Other studies could also be important to order depending on what is uncovered in the steps above. For men with hair loss, such tests are not always needed.

A scalp biopsy is rarely needed. With a properly obtained history and a properly conducted scalp exam, a biopsy becomes redundant for many patients. However, a biopsy is helpful in challenging cases and helpful in some scarring alopecias to confirm the subtype.


R= Repeat if necessary.

It's usually possible to diagnose hair loss with the first three steps above : history, assessment and investigations. However, there are some situations where it's just not.  In such challenging cases, the only way to definitively understand the cause of the patient's hair loss is to see them back in the office and 'follow' their hair growth and hair loss over a period of time. Sometimes this is 2 months and other times it could be 6 months.  At each visit, the steps of history taking (H), assessment (A) and investigations (I) may be repeated. 

Exceptions to the HAIR Rule

There are not many exceptions. A history of hair loss and an assessment is always required. There are many mimickers of hair loss. A photo of a patient with what looks like genetic hair loss could be genetic hair loss. But without a history one can not be certain.  Investigations, as stated above, are not always needed. 


The "H.A.I.R." Principle is a helpful memory tool to remind both physicians and patients that diagnosing hair loss might not always be quick and easy.  A carefully obtained medical history, a thorough scalp assessment and a variety of investigations need to be part of the evaluation. In some cases where the diagnosis is elusive, these steps need to be repeated in a few months 

Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887

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