The Air Force is looking to expand its ranks in part by boosting the number medical waivers for potential recruits, the service announced Tuesday.

Prospective airmen routinely disqualified from serving because of eczema, asthma and Attention Deficit Hyperactivity Disorder, or ADHD, will now be given a second chance on a case-by-case basis.

Rules blocking recruits who have prior marijuana use will also be relaxed.

"As medical capabilities have improved and laws have changed, the Air Force is evolving so we are able to access more worldwide deployable Airmen to conduct the business of our nation," Air Force Chief of Staff Gen. David Goldfein said in a statement.

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Individuals with these conditions will not need extra medical check-ups. "They'll just [need to] meet the same annual preventive assessment that all airmen get," Lt. Gen (Dr.) Mark Ediger, the Air Force's surgeon general, told Military.com on Friday.

"When airmen apply for enlistment or commissioning in the Air Force working with a recruiter, they go to a military entrance processing station, or MEPS, to get a medical history and a physical … and if they give a history of a condition that may represent something of concern, maybe disqualifying, then we'll ask the individual to provide medical records" voluntarily, Ediger said in an interview at the Pentagon.

If medical records do not help clarify their history, military physicians may perform a secondary evaluation.

"These airmen will be worldwide deployable the day they come in the door and be able to perform any mission the Air Force needs them to," said Lt. Gen. Gina Grosso, deputy chief of staff for Air Force manpower, personnel and services.

"We are always looking at our policies and, when appropriate, adjusting them to ensure a broad scope of individuals are eligible to serve," said outgoing Chief Master Sergeant of the Air Force James Cody.

"These changes allow the Air Force to aggressively recruit talented and capable Americans who until now might not have been able to serve our country in uniform," he said in a statement.

Here's the new medical breakdown:

Prior marijuana use

The Air Force will still have a zero tolerance policy when it comes to airmen smoking or using marijuana, but how many days, weeks or months prior to enlisting that a potential airman used will no longer be a limiting factor.

The service is no longer considering how long it has been since an airman used marijuana prior to service in a move to "standardize" the questions asked of potential recruits.

Air Force admission sources were inconsistent on what timeframe was acceptable for prior marijuana use.

"Standards of pre-accession marijuana use were different for getting into the Air Force Academy vs. Air Force Recruiting Service for enlistment or officer training school vs. AFROTC," said Air Force spokesman Zachary Anderson.

"We didn't ask the same questions," Grosso said. "Some recruiters used if you smoked marijuana less than five times, sometimes it was less than 15 times."

States legalizing recreational marijuana in one form or another -- Colorado, Alaska, California, Maine, Massachusetts, Nevada, Oregon, Washington, and the District of Columbia -- made the Air Force question, "How should we think about that?" Grosso said.

"What we decided to do is stop asking [about] prior marijuana use at the recruiter level," she said, because "first of all, who really counts how many times they've used marijuana? So that just comes off the table."

Grosso reiterated that once a recruit enters the process of becoming an airman, any marijuana use detected will automatically cause him or her to be separated from service.

"We do not have any waivers for that," she said. "And any drug dependency which we determine through a different procedure is also fully disqualifying."

Ediger said a diagnosed substance abuse disorder -- not limited to marijuana -- will also preclude service.

"Through the [MEPS], there are some evidence-based screening questionnaires that can be used to screen for that disorder," Ediger said. "Any condition that would require prescription of medical marijuana would probably be a disqualifying condition to begin with."

The MEPS screening is not just for marijuana -- it looks for opioids or the abuse of prescription pain drugs for recreational purposes.

A run-in with the law in a state where marijuana is illegal is also a disqualifying factor, Grosso said.

The Air Force routinely and randomly screens its airmen per rules outlined in the drug demand reduction program policy.

Asthma

Under the previous policy, if a potential recruit's history showed he or she required periodic or significant treatment for wheezing, there was a presumption it was asthma.

"The change to the policy on asthma: We're going to use some diagnostic testing to actually determine if a particular applicant has asthma where the history is questionable -- a relatively frequent occurrence where somebody at some point during their youth required treatment for wheezing, but sometimes it's not really asthma," Ediger said.

For example, an infection or an unusual exposure manifesting with similar symptoms can sometimes be misdiagnosed as asthma.

"What the policy says now is we're going to use a Methacholine challenge test," or a type of lung function test that determines if an individual's airway is prone to spasms, and "it will trigger the spasm, and then we have a breathing test to measure that," he said.

"If the test is normal, we will not regard that applicant as having asthma and there's no qualification question," Ediger said. "Previously, we did not offer the test."

Candidates who successfully pass this test will be processed for a waiver, the new policy states.

Those with a verified diagnosis of prolonged asthma remain unqualified to serve.

Ediger said while the service has not necessarily seen an increase in asthma cases, there "has always been a significant number of applicants who had some history of wheezing or an actual diagnosis … but I think the frequency which we see that really parallels the prevalence of asthma in the U.S. population."

According to the Centers for Disease Control's 2014 National Health Interview Survey, 17.7 million American adults have asthma. About 6.3 million children also have the medical condition, the survey says.

"There is a legitimate concern, because of the range of environments we expose our airmen to. Triggering a severe asthma attack in a remote environment … could be quite hazardous," Ediger said.

Eczema

Eczema is a skin inflammation often associated with allergies and affects roughly 30 percent of the population.

"It is disqualifying … per [Defense Department] guidance," Ediger said, "but the Air Force has waiver authority" over the condition, also known as Dermatitis.

Few waivers have been granted in the past for airmen whose medical history suggested they tested positive for the disease, even if they showed no overt symptoms, he said.

Ediger said officials reconsidered giving out waivers because of airmen with eczema currently serving -- in many ways, "we were able to treat and control their eczema."

"We found they were very successful in deploying -- it was extremely rare for them to require early termination … and so based on that review, we made the determination that for those with a history of eczema that was no longer active or currently active, mild eczema … that we will allow them to come into the Air Force," he said.

Certain occupational restrictions may still apply for personal and mission safety, according to the new policy.

"We know, for certain occupations, the skin is exposed to chemical solvents, extreme temperatures," Ediger said, "and rather than put that airman into a job that is highly likely to aggravate their eczema," the service will review the best fit.

Some blocked occupations may include aircraft maintainers, civil engineering and some jobs under Air Force Special Operations Command, he said.

Recruits with eczema who qualify for service will be notified by a recruiter they may not qualify for certain career fields, Ediger said.

The Air Force said the list of jobs will evolve over time and could not provide a set list at press time.

ADHD

A potential airman with a history of Attention Deficit Hyperactivity Disorder must demonstrate at least 15 months of performance stability -- either academic or through the individual's occupation -- off medication for the condition immediately preceding enlistment or enrollment, according to the new policy.

Previously, if an individual was ever treated for ADHD as a child and especially into adolescence, he or she was disqualified from military service under DoD policy. The department relaxed some rules in 2010, and further amended how it granted waivers in 2015, stating, "Each service's waiver authority for medical conditions will make a determination based on all available information regarding the issue or condition."

Like its sister services, the Air Force is willing to consider a waiver.

If an individual took a prescription for ADHD after the age of 14, "we needed to see a period of 24 months of demonstrated stability off medication before we considered them for a waiver" to join, Ediger said of the previous policy.

Recent studies suggest there has been a spike in school-age children or young adults needing medication for ADHD. "We're not sure why," he said.

More than one in 10 children received an ADHD diagnosis in 2011 and were treated by therapy, medication or both, according to a CDC study published in 2015 featured in Psychology Today.

"Looking at our experience, we saw that, of those airmen with a history of ADHD we had waived into the Air Force, that they had a very high success rate in completing their training and moving on to serve as airmen," Ediger said. "So we determined we can shorten the period of demonstrated stability from 24 months down to 15 months."

Airmen must still abide by rules as outlined in the DoD's Medical Standards for Appointment, Enlistment, or Induction in the Military Services, or DoDI 6130.03, the Air Force said.

Ediger said officials will continue to monitor previously diagnosed airmen, "and we'll consider further modifications based on what occurs with the airmen we waive in."

Editors note: This story has been updated to clarify that accessioning sources were inconsistent on the rules for prior marijuana use.

-- Oriana Pawlyk can be reached at oriana.pawlyk@military.com. Follow her on Twitter at @Oriana0214.